WO2016084318A1 - Inspection object information acquiring apparatus - Google Patents

Inspection object information acquiring apparatus Download PDF

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Publication number
WO2016084318A1
WO2016084318A1 PCT/JP2015/005598 JP2015005598W WO2016084318A1 WO 2016084318 A1 WO2016084318 A1 WO 2016084318A1 JP 2015005598 W JP2015005598 W JP 2015005598W WO 2016084318 A1 WO2016084318 A1 WO 2016084318A1
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WO
WIPO (PCT)
Prior art keywords
inspection object
acoustic wave
detecting element
wave detecting
unit
Prior art date
Application number
PCT/JP2015/005598
Other languages
French (fr)
Inventor
Yukio Furukawa
Toru Imai
Yasufumi Asao
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Canon Kabushiki Kaisha
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Publication of WO2016084318A1 publication Critical patent/WO2016084318A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/22—Details, e.g. general constructional or apparatus details
    • G01N29/24—Probes
    • G01N29/2418—Probes using optoacoustic interaction with the material, e.g. laser radiation, photoacoustics
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/0093—Detecting, measuring or recording by applying one single type of energy and measuring its conversion into another type of energy
    • A61B5/0095—Detecting, measuring or recording by applying one single type of energy and measuring its conversion into another type of energy by applying light and detecting acoustic waves, i.e. photoacoustic measurements
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/48—Other medical applications
    • A61B5/4887—Locating particular structures in or on the body
    • A61B5/489—Blood vessels
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/1702—Systems in which incident light is modified in accordance with the properties of the material investigated with opto-acoustic detection, e.g. for gases or analysing solids
    • G01N2021/1708—Systems in which incident light is modified in accordance with the properties of the material investigated with opto-acoustic detection, e.g. for gases or analysing solids with piezotransducers

Definitions

  • the present invention relates to an inspection object information acquiring apparatus that uses a photoacoustic effect.
  • the optical imaging apparatus irradiates an inspection object with light from a light source such as a laser, and forms an image of information on the inside of the inspection object acquired on the basis of the incident light.
  • the optical imaging technique includes photoacoustic tomography (PAT).
  • PAT irradiates an inspection object with pulsed light generated from a light source and detects an acoustic wave generated from a tissue absorbing the energy of the pulsed light propagating through and diffused in the inspection object.
  • the phenomenon of the generation of a photoacoustic wave is called photoacoustic effect.
  • the acoustic wave generated by the photoacoustic effect is called photoacoustic wave.
  • An inspection portion such as a tumor or a blood vessel, typically has a higher absorptance for optical energy than that of its peripheral tissue. Hence, the inspection portion absorbs more light than the peripheral tissue does, and instantly expands.
  • a probe hereinafter, referred to as photoacoustic wave detecting element
  • a sound pressure distribution of the photoacoustic wave generated by the photoacoustic effect in the inspection object can be imaged (hereinafter, referred to as photoacoustic wave image).
  • an optical characteristic distribution or more particularly a light absorption coefficient distribution of the inside of the inspection object can be acquired.
  • These pieces of information can be used for quantitative measurement for a specific substance in the inspection object, for example, glucose or hemoglobin, contained in the blood.
  • NPL 1 suggests an ultrasonic focus photoacoustic microscope that can image an image of a blood vessel present in a region near the skin with high resolution by using an acoustic lens.
  • NPL 1 In the photoacoustic microscope, it is important to recognize the measurement position on the surface of a living body.
  • NPL 1 since an ultrasonic detecting element and an optical system are arranged above the living body, it is difficult to observe the surface of the living body by using a camera. Also, for example, if an inspection object is measured in a wider range, it has been difficult to correctly recognize the measurement position in the measurement range.
  • the present invention is made in light of the above-described situations, and the present invention provides an inspection object information acquiring apparatus that can correctly recognize the measurement position on a surface of an inspection object in a wide range.
  • the present invention provides an inspection object information acquiring apparatus including a light source; an optical element configured to collect light emitted from the light source; an acoustic wave detecting element configured to detect an acoustic wave, which is generated when an inspection object is irradiated with the light collected by the optical element, and output an electrical signal; an acoustic lens located between a receiving surface for the acoustic wave of the acoustic wave detecting element and the inspection object; a signal processing unit configured to acquire information on the inspection object from the electrical signal; an image pickup unit configured to capture an image of the inspection object; and a scanning unit configured to cause the acoustic wave detecting element and the image pickup unit to scan the inspection object.
  • the scanning unit causes the acoustic wave detecting element and the image pickup unit to scan the inspection object while holding a positional relationship between the acoustic wave detecting element and the image pickup unit.
  • the measurement position of the inspection object can be correctly recognized in the wide range.
  • Fig. 1 is a schematic view of a first embodiment.
  • Fig. 2 is an illustration explaining a measurement flow of the first embodiment.
  • Fig. 3 is a schematic view of a second embodiment.
  • Fig. 4A illustrates a relationship between acquired images and displayed images of the second embodiment.
  • Fig. 4B illustrates the relationship between the acquired images and the displayed images of the second embodiment.
  • Fig. 5 is an illustration explaining a measurement flow of the second embodiment.
  • Fig. 6 is a schematic view of a third embodiment.
  • Fig. 7 illustrates a relationship of a position indication mark of a displayed image of the third embodiment.
  • Fig. 8 is an illustration explaining a measurement flow of the third embodiment.
  • An inspection object information acquiring apparatus is briefly described with reference to Fig. 1, and then respective embodiments are described below.
  • the inspection object information acquiring apparatus includes a light source 100, and a truncated conical mirror 109 being an optical element configured to collect light emitted from the light source 100.
  • the apparatus further includes an acoustic wave detecting element 113 configured to detect an acoustic wave, which is generated when an inspection object 133 is irradiated with the light collected by the truncated conical mirror 109 being the optical element, and output an electrical signal.
  • the apparatus also includes an acoustic lens 115 located between a receiving surface 114 of the acoustic wave detecting element 113 and the inspection object 133.
  • the apparatus also includes a signal processing unit 126 configured to acquire information on the inspection object 133 from the electrical signal output from the acoustic wave detecting element 113.
  • the apparatus also includes an observation camera 117 being an image pickup unit configured to capture an image of a surface of the inspection object 133.
  • the apparatus further includes an X-axis stage 121 and a Y-axis stage 123 being scanning units configured to cause the acoustic wave detecting element 113 and the observation camera 117 being the image pickup unit to scan the inspection object 133.
  • the scanning units cause the acoustic wave detecting element 113 and the observation camera 117 being the image pickup unit to scan the inspection object 133 while holding the positional relationship between the acoustic wave detecting element 113 and the observation camera 117 being the image pickup unit. Accordingly, a measurement position of the inspection object can be correctly recognized in a wide range. This configuration is described below.
  • an inspection object information acquiring apparatus that uses a photoacoustic effect, such as a photoacoustic microscope, when a photoacoustic wave is received, it is important to recognize the measurement position on a surface of an inspection object. Owing to this, there is an idea of providing an image pickup unit, such as a camera, in the inspection object information acquiring apparatus to recognize the measurement position of the inspection object.
  • an image pickup unit such as a camera
  • the acoustic wave detecting element scans the inspection object to measure the inspection object in a wide rage in the inspection object information acquiring apparatus, since the positional relationship between the inspection object and the acoustic wave detecting element is changed with time, it is difficult to correctly recognize the measurement position of the inspection object.
  • the measurement position can be more correctly recognized on the basis of the previously determined distance between the acoustic wave detecting element 113 and the observation camera 117.
  • the inspection object 133 has a surface shape with protrusions and depressions, information in the depth direction can be easily acquired, and hence information on the surface of the inspection object can be stereoscopically recognized.
  • the wavelength of the light source to be used in the embodiment of the invention is desirably a wavelength with which light propagates to the inside of an inspection object.
  • the light source emits light with a wavelength with which the light is absorbed by a specific component among components configuring the living body.
  • a desirable wavelength is in a range from 500 nm to 1200 nm.
  • the light can be pulsed light, and the pulse width is preferably in a range from several nanoseconds to about 100 nanoseconds.
  • the light source may use a laser, a light-emitting diode, or a flash lamp.
  • the laser can use any of various lasers including a solid-state laser, a gas laser, a dye laser, and a semiconductor laser.
  • the light emitted from the light source is desirably transmitted by a light transmitting unit and emitted on the inspection object.
  • the light transmitting unit desirably uses a multimode optical fiber.
  • An irradiation optical system including the above-described truncated conical mirror, irradiates the inspection object, such as a living body, with the light transmitted by the light transmitting unit.
  • the irradiation optical system is configured of a collimate lens, a conical lens, and the truncated conical mirror being the above-described optical element, and is arranged so that the optical path of the irradiation optical system does not interfere with the acoustic wave detecting element or the observation camera.
  • the truncated conical mirror has a hollow structure in which a center portion is hollowed in a cylindrical shape so that the acoustic wave detecting element can be arranged.
  • the acoustic wave detecting element receives a photoacoustic wave generated at the surface of the inspection object and in the inspection object due to the emitted pulsed light, and converts the photoacoustic wave into an electrical signal (a reception signal) being an analog signal.
  • Any acoustic wave detecting element may be used as long as the unit can detect an acoustic wave signal.
  • a unit using a piezoelectric phenomenon, a unit using an optical resonance, or a unit using a change in capacitance may be used.
  • the acoustic lens is provided so as to selectively receive an acoustic wave from a desirable focal point. In the embodiment in Fig.
  • the normal-line direction is uniquely determined.
  • the receiving surface for the acoustic wave is not a flat surface, for example, if the surface is a curved surface, a synthetic vector, which is acquired by drawing normal lines from respective points (representative several discrete points) of the curved surface and adding the normal lines together as a vector, may serve as the normal line.
  • the synthetic vector is equivalent to the normal line extending from the center of the hemisphere.
  • the observation camera is an image pickup unit and optically observes the surface of the inspection object.
  • a captured camera image (a visible light image) that is captured is displayed on a monitor 163 being a display unit, and hence a measurement portion is easily selected.
  • An object plane of the observation camera being the image pickup unit and a focal position of the acoustic wave detecting element are desirably aligned with each other in the Z direction or separated from each other by a predetermined distance. For example, to acquire information on a portion near the surface of the inspection object, adjustment may be made such that the focal position of the acoustic wave detecting element is aligned with the object plane of the observation camera.
  • an optical axis 157 of the observation camera 117 being the image pickup unit represents an image pickup direction.
  • the image is desirably captured with illumination with illumination light.
  • White illumination may be used for capturing a natural image to determine an image capturing position.
  • illumination light of a single color may be used depending on the purpose of use.
  • illumination light other than visual light such as ultraviolet light or infrared light, may be used depending on the purpose of use as long as the sensitivity of the observation camera is ensured.
  • the illumination light desirably uniformly illuminates the inspection object.
  • light with a known geometric light and dark pattern such as a mesh pattern, may be emitted for image analysis (described later).
  • a housing also serves as a supporting unit configured to support the acoustic wave detecting element and the observation camera being the image pickup unit.
  • the acoustic wave detecting element and the observation camera are fixed with a predetermined gap in the X direction.
  • the acoustic wave detecting element 113 and the observation camera 117 being the image pickup unit are integrally supported by the housing.
  • the housing being the supporting unit as shown in Fig. 1 supports the acoustic wave detecting element and the image pickup unit so that a normal-line direction 150 of the receiving surface 114 of the acoustic wave detecting element 113 and the optical axis 157 of the observation camera 117 being the image pickup unit are substantially parallel to each other.
  • the axis during image capturing of an inspection object image acquired by the observation camera is aligned with the axis during image capturing of an inspection object information image acquired by the acoustic wave detecting element and a signal processing unit (described later).
  • the illumination optical system is also supported by the supporting unit. Since a housing 101 being the supporting unit integrally supports the acoustic wave detecting element 113 and the observation camera 117 being the image pickup unit, the positional relationship between the acoustic wave detecting element 113 and the observation camera 117 being the image pickup unit is easily held during scanning.
  • the scanning unit includes the X-axis stage 121 and the Y-axis stage 123, and causes the acoustic wave detecting element 113 and the observation camera 117 to scan the inspection object 133 while holding the positional relationship between the acoustic wave detecting element 113 and the observation camera 117.
  • the housing 101 being the supporting unit executes scanning one-dimensionally, two-dimensionally, or three-dimensionally along the inspection object 133.
  • the scanning direction of the acoustic wave detecting element 113 and the observation camera 117 being the image pickup unit with respect to the inspection object 133 may be a direction from the acoustic wave detecting element 113 to the image pickup unit (in Fig. 1, the positive X direction). Accordingly, although described later, the positional alignment between the inspection object image acquired by the observation camera 117 and the acoustic wave detecting element is easily executed.
  • a signal collecting unit collects the electrical signal acquired by the acoustic wave detecting element.
  • the signal collecting unit desirably includes an A/D converter that converts an analog signal into a digital signal.
  • the signal processing unit generates a two-dimensional or three-dimensional photoacoustic wave image or an optical characteristic distribution of the inside of the inspection object from the electrical signal collected by the signal collecting unit.
  • the photoacoustic wave image can be generated by detecting the electrical signal by envelope detection and replacing a signal value per time into a signal value in the depth direction of the inspection object.
  • An image recording unit records the inspection object image information acquired by the observation camera.
  • the inspection object image information recorded in the recording unit may be in any of various forms, such as still image information, continuous image information on still images during scanning, and movie information during scanning.
  • An image processing unit generates an image to be displayed on the display unit.
  • the image processing unit causes the display unit to display the inspection object information acquired by the signal processing unit and the inspection object image information captured by the observation camera 117 being the image pickup unit.
  • the positional relationship between the acoustic wave detecting element and the observation camera is previously determined. Hence, an image corresponding to the position of the acoustic wave detecting element can be displayed by displaying recorded continuous images with a temporal delay.
  • the inspection object image information relating to a portion of the inspection object located in front of the acoustic wave detecting element can be displayed on the display unit, from among the inspection object image information recorded in the recording unit, during scanning of the acoustic wave detecting element and the image pickup unit on the inspection object. Also, the still image information on the inspection object recorded in the recording unit and a position indication mark indicative of the position of the acoustic wave detecting element during scanning may be displayed in a superposed manner.
  • the observation camera can acquire inspection object image information at a plurality of different positions.
  • information in the depth direction can be acquired by using a known calculation method of stereoscopy based on the principle of triangulation from images acquired at two different positions. That is, the stereoscopic shape of the inspection object can be calculated and acquired.
  • the stereoscopic shape of the inspection object can be calculated on the basis of a plural pieces of inspection object image information relating to different portions of the inspection object recorded in the recording unit. It is known that the stereoscopy provides a higher precision as the number of viewpoints to be used for calculation is larger.
  • highly precise three-dimensional shape data (stereoscopic shape data) can be acquired.
  • the stereoscopic shape of the inspection object is acquired by the image processing unit.
  • a stereoscopic shape acquiring unit configured to calculate the stereoscopic shape of the inspection object may be provided.
  • the scanning unit may cause the acoustic wave detecting element 113 and the observation camera 117 to scan the inspection object while changing the position of the acoustic wave detecting element 113 in a focal length direction based on information on the stereoscopic shape of the inspection object acquired by the stereoscopic shape acquiring unit. Accordingly, for example, the surface of the surface can be more correctly measured.
  • the display unit displays the information on the inspection object acquired by the signal processing unit and the information on the inspection object image captured by the observation camera 117 being the image pickup unit.
  • the display unit may use a typical flat-screen display element. Also, a known three-dimensional display element for displaying the above-described stereoscopic image may be used.
  • a scanning-range input unit is configured to input a scanning range of the acoustic wave detecting element 113 and the observation camera 117 being the image pickup unit by the scanning unit for the inspection object 133.
  • the scanning-range input unit inputs a scanning range based on the image of the observation camera displayed on the display unit. Actual scanning is executed with regard to the distance between the acoustic wave detecting element and the observation camera.
  • a scanning control unit controls a mechanical scanning range in a horizontal plane for the inspection object according to the scanning-range input unit.
  • a mechanism configured to adjust the distance between the housing and the inspection object to a proper distance in accordance with the information on the above-described three-dimensional shape (stereoscopic shape) may be further provided.
  • the above-described configuration is a configuration desirable for the inspection object information acquiring apparatus according to this embodiment of the invention.
  • Fig. 1 is a conceptual diagram explaining a first embodiment of an inspection object information acquiring apparatus of the invention.
  • reference sign 100 denotes a pulse light source configured of an optical parametric oscillator (OPO) laser that generates pulsed light with a wavelength of 800 nm, a pulse width of 5 nsec, and a repetition frequency of 100 Hz.
  • Reference sign 103 denotes an optical fiber. The optical fiber 103 functions as the light transmitting unit.
  • Reference sign 105 denotes a condenser lens, 107 denotes a conical lens, and 109 denotes a truncated conical mirror configuring an irradiation optical system.
  • Reference sign 111 denotes light emitted from the optical fiber 103.
  • Respective components of the irradiation optical system are arranged so that the light 111 passes through the irradiation optical system and is collected at a desirable position.
  • Reference sign 113 denotes an acoustic wave detecting element using lead zirconate titanate (PZT) as a piezoelectric material and having a center frequency of 50 Hz
  • 115 denotes an acoustic lens provided at a distal end of the acoustic wave detecting element 113.
  • PZT lead zirconate titanate
  • Reference sign 117 denotes an observation camera 117
  • 119 denotes an image forming lens provided at a distal end of the observation camera 117.
  • Reference sign 101 denotes a housing.
  • the housing 101 integrally supports the irradiation optical system, the acoustic wave detecting element 113, and the observation camera 117.
  • the housing 101 is connected to an X-axis stage 121 and a Y-axis stage 123 through a support arm 125.
  • the X-axis stage 121 and the Y-axis stage 123 are electrically connected to a scanning control unit 127, and can cause the housing 101 to execute scanning.
  • the housing being the supporting unit integrally supports the acoustic wave detecting element 113 and the observation camera 117
  • scanning is executed while the positional relationship between the acoustic wave detecting element 113 and the observation camera 117 is held.
  • Reference sign 133 denotes the inspection object.
  • the inspection object 133 is placed on a support table 131. Although not illustrated, the inspection object 133 and the support table 131 are movable in the Z direction.
  • Reference sign 153 denotes side walls, and 151 denotes a thin film.
  • a water tank surrounded by the side walls 153 and the thin film 151 is filled with water 155.
  • the thin film 151 is configured of a material that transmits light and ultrasound.
  • a photoacoustic wave (not indicated in the drawing) generated from the inspection object 133 as the result of the irradiation with the light 111 propagates through the thin film 151 and the water 155, and reaches the acoustic wave detecting element 113 through the acoustic lens 115.
  • the acoustic wave detecting element 113 receives the photoacoustic wave and converts the photoacoustic wave into an electrical signal being an analog signal.
  • the photoacoustic wave generated from the focal position can be selectively received.
  • the position in the Z direction of the inspection object 133 is adjusted so that an observation subject portion of the inspection object 133 is located near the focal point.
  • This adjustment may be made so that the focal point of the acoustic wave detecting element is located on a plane extending from the object plane of the observation camera 117 being the image pickup unit or located at a position separated from the plane extending from the object plane of the observation camera 117 by a predetermined distance.
  • the object plane of an observation camera (the focal point plane of an observation camera) can be aligned with a surface of an inspection object.
  • the above-described positional arrangement may be that the focal point of the acoustic wave detecting element is located at the surface of the inspection object, or located at a position separated from the surface of the inspection object by a predetermined distance (the inside of the inspection object).
  • the received electrical signal is collected by a signal collecting unit (not indicated in the drawing).
  • the acoustic wave detecting element 113 executes one-dimensional or two-dimensional scanning, and executes the irradiation with light and the collection of signals in synchronization with the scanning of the acoustic wave detecting element 113. Then, a signal processing unit 126 generates a two-dimensional or three-dimensional photoacoustic wave image of the inside of the inspection object from the collected electrical signal.
  • the image forming lens 119 provided at the distal end of the observation camera 117 includes an air region therein, and is arranged so that the outside of the image forming lens 119 is dipped in the water 155.
  • the positions of the observation camera 117 and the image forming lens 119 are adjusted so that the image of the surface of the inspection object 133 is formed on an image pickup element of the camera through the water 155.
  • Reference sign 161 denotes an image storage unit.
  • the image storage unit 161 stores the image acquired by the observation camera 117, and further displays the image on the monitor 163.
  • Reference sign 165 denotes a scanning-range input unit 165.
  • the scanning-range input unit 165 inputs a scanning range of the acoustic wave detecting element determined on the basis of the image of the observation camera 117 displayed on the monitor 163.
  • the scanning control unit 127 controls the housing 101 based on the input scanning range.
  • An image of an inspection object acquired by the observation camera 117 is displayed on the monitor 163.
  • a measurement position and a measurement range are determined.
  • the measurement position and the measurement range are input by the input unit 165.
  • the acoustic wave detecting element 113 is moved to a desirable position based on the input measurement position and measurement range. At this time, while the distance between the acoustic wave detecting element 113 and the observation camera 117 is held, the position on the acquired image and the position of the acoustic wave detecting element 113 are aligned with regard to the distance between the acoustic wave detecting element 113 and the observation camera 117.
  • a photoacoustic wave is received, and the photoacoustic wave is converted into an electrical signal.
  • the electrical signal is collected.
  • Step S1005 and Step S1006 are repeated.
  • a photoacoustic wave image of the inside of the inspection object is generated.
  • the surface of the inspection object can be observed in a wide range, and the position of the photoacoustic wave detecting element can be easily figured out from the image of the surface of the inspection object. Accordingly, the measurement position can be more correctly recognized. That is, since the acoustic wave detecting element and the observation camera scan the inspection object while the positional relationship between the acoustic wave detecting element and the observation camera is held, measurement with the acoustic wave detecting element at a portion constantly separated from the center of the image of the surface of the inspection object by a predetermined distance can be recognized. It is desirable to display a scale on the image of the surface of the inspection object so that the measurement position can be more correctly recognized.
  • a second embodiment of the invention is described with reference to Fig. 3.
  • the same number is applied to the same portion as that in Fig. 1, and the description thereof is omitted.
  • the difference from the first embodiment is that an image by the observation camera acquired at the same position as the measurement position of the acoustic wave detecting element is displayed on the monitor during scanning.
  • reference sign 201 denotes an image recording unit.
  • the image recording unit 201 has a function of continuously recording images (a movie) acquired by the observation camera 117.
  • Reference sign 203 denotes an image processing unit.
  • the image processing unit 203 has a function of acquiring positional information of the acoustic wave detecting element 113 from a scanning control unit 227, selecting an image in the case in which the observation camera 117 is located at the position from the image recording unit 201, and displaying the image on the monitor 163.
  • the distance between the acoustic wave detecting element 113 and the observation camera 117 is previously determined. If the housing 101 scans at a constant speed in a direction from the acoustic wave detecting element 113 to the observation camera 117 (the positive X direction in Fig. 3), first, the observation camera 117 passes through a certain point of the inspection object 133, and then the acoustic wave detecting element 113 passes through the same point with a delay of a constant time. Accordingly, by continuously recording the images by the observation camera 117 and displaying the images on the monitor 163 with the delay of the constant time, the image on the monitor and the acquired inspection object information apparently correspond to each other.
  • Fig. 4A illustrates a series of images acquired by the observation camera 117 when scanning is provided in the positive X direction.
  • Fig. 4B illustrates a series of images displayed on the monitor 163.
  • Fig. 3 illustrates the case on one-dimensional (X direction) scanning. If two-dimensional scanning is executed, scanning is provided in the positive X direction first, then, movement is provided in the Y direction by a predetermined distance, the X position is returned to the start position, and then scanning may be provided in the position X direction again.
  • An image acquired by the observation camera 117 is displayed on the monitor 163.
  • a measurement position and a measurement range are determined.
  • the measurement position and the measurement range are input by the input unit 165.
  • the acoustic wave detecting element 113 is moved to a desirable position based on the input measurement position and measurement range. At this time, the distance between the acoustic wave detecting element 113 and the observation camera 117 is considered so that the observation camera 117 can acquire an image in a measurement range of an actual inspection object.
  • the acoustic wave detecting element 113 scans at a constant speed.
  • Reception of a photoacoustic wave and conversion of the photoacoustic wave into an electrical signal are started when the acoustic wave detecting element 113 enters the measurement range.
  • An image corresponding to the position of the acoustic wave detecting element 113 is displayed on the monitor 163.
  • the electrical signal is collected.
  • Step S2005 to Step S2009 are repeated.
  • a photoacoustic wave image of the inside of the inspection object is generated.
  • the measurement position can be more correctly recognized. For example, if the monitor 163 is observed while the inspection object information acquired by the acoustic wave detecting element 113 is displayed on an oscilloscope, for example, it can be visually recognized that the signal intensity increases when the acoustic wave detecting element 113 approaches an absorber. Accordingly, the measurement position can be more correctly recognized.
  • a third embodiment of the invention is described with reference to Fig. 6.
  • the same number is applied to the same portion as that in Fig. 1, and the description thereof is omitted.
  • the difference from the first embodiment is that a position indication mark indicative of the measurement position by the acoustic wave detecting element is superposed on an image by the observation camera, and the position indication mark and the image are displayed on the monitor during scanning.
  • the second embodiment is effective if the measurement range is larger than the range of the image on the monitor. In other words, if the range of the image on the monitor is larger than the measurement range, it is not meaningful that the image is displayed while being moved depending on the position of the acoustic wave detecting element. This embodiment is effective in such a case.
  • reference sign 301 denotes an image processing unit.
  • the image processing unit 301 has a function of acquiring positional information of the acoustic wave detecting element 113 from the scanning control unit 227, superposing a position indication mark indicative of the measurement position by the acoustic wave detecting element on an image recorded in the image storage unit 161, and displaying the image on the monitor 163.
  • reference sign 303 denotes an image recorded in the image storage unit 161.
  • reference sign 305 denotes a position indication mark generated on the basis of the positional information of the acoustic wave detecting element 113 from the scanning control unit 227, and indicates the measurement position by the acoustic wave detecting element.
  • Reference sign 307 denotes an arrow indicative of the state of movement of the position indication mark 305. The arrow 307 is not actually displayed on the monitor.
  • the image 303 and the position indication mark 305 are displayed on the monitor 163 in a superposed manner.
  • An image acquired by the observation camera 117 is displayed on the monitor 163.
  • a measurement position and a measurement range are determined.
  • the measurement position and the measurement range are input by the input unit 165.
  • the acoustic wave detecting element 113 is moved to a desirable position based on the input measurement position and measurement range. At this time, the position on the acquired image and the position of the acoustic wave detecting element 113 are aligned with regard to the distance between the acoustic wave detecting element 113 and the observation camera 117.
  • the acoustic wave detecting element 113 scans at a constant speed.
  • a position indication mark indicative of the position of the acoustic wave detecting element 113 is superposed on the image displayed in Step S3001 and displays the position indication mark and the image on the monitor 163.
  • the electrical signal is collected.
  • Step S3005 to Step S3008 are repeated.
  • a photoacoustic wave image of the inside of the inspection object is generated.
  • the measurement position can be more correctly recognized.
  • a fourth embodiment of the invention is described with reference to Fig. 6.
  • the difference from the first to third embodiments is that information in the depth direction with respect to the camera is acquired by using image information of the observation camera at a plurality of positions.
  • the observation camera 117 scans, and acquires images at two or more different positions.
  • a three-dimensional shape (a stereoscopic shape) of a surface of an inspection object is acquired by calculation.
  • a projection image from the front is displayed on the monitor 163.
  • a measurement position and a measurement range are determined.
  • the measurement position and the measurement range are input by the input unit 165.
  • the acoustic wave detecting element 113 is moved to a desirable position based on the input measurement position and measurement range. At this time, the position on the acquired image and the position of the acoustic wave detecting element 113 are aligned with regard to the distance between the acoustic wave detecting element 113 and the observation camera 117.
  • the acoustic wave detecting element 113 scans. At this time, based on the information in the depth direction acquired by calculation, scanning is provided while the constant distance is held between the acoustic wave detecting element and the inspection object. In other words, by changing the position of the acoustic wave detecting element in the focal point direction, scanning is provided while the constant distance is held between the acoustic wave detecting element and the inspection object.
  • the electrical signal is collected.
  • Step S4007 to Step S4009 are repeated.
  • a photoacoustic wave image of the inside of the inspection object is generated.
  • a sample is constantly held within a depth of field.
  • a sharp image can be acquired.
  • the focal point of the acoustic wave detecting element can be constantly set at the surface of the inspection object. More correct measurement can be realized.

Abstract

An inspection object information acquiring apparatus includes an optical element configured to collect light emitted from a light source; an acoustic wave detecting element configured to detect an acoustic wave generated by irradiation of an inspection object with the light and output an electrical signal; an acoustic lens located at a receiving surface for the acoustic wave; a signal processing unit configured to acquire information on the inspection object from the electrical signal; an image pickup unit configured to capture an image of the inspection object; and a scanning unit configured to cause the acoustic wave detecting element and the image pickup unit to scan the inspection object. The scanning unit causes the acoustic wave detecting element and the image pickup unit to scan the inspection object while holding a positional relationship between the acoustic wave detecting element and the image pickup unit.

Description

INSPECTION OBJECT INFORMATION ACQUIRING APPARATUS
The present invention relates to an inspection object information acquiring apparatus that uses a photoacoustic effect.
A study on an optical imaging apparatus is being actively promoted in medical fields. The optical imaging apparatus irradiates an inspection object with light from a light source such as a laser, and forms an image of information on the inside of the inspection object acquired on the basis of the incident light. The optical imaging technique includes photoacoustic tomography (PAT). PAT irradiates an inspection object with pulsed light generated from a light source and detects an acoustic wave generated from a tissue absorbing the energy of the pulsed light propagating through and diffused in the inspection object. The phenomenon of the generation of a photoacoustic wave is called photoacoustic effect. The acoustic wave generated by the photoacoustic effect is called photoacoustic wave. An inspection portion, such as a tumor or a blood vessel, typically has a higher absorptance for optical energy than that of its peripheral tissue. Hence, the inspection portion absorbs more light than the peripheral tissue does, and instantly expands. A probe (hereinafter, referred to as photoacoustic wave detecting element) detects a photoacoustic wave that is generated at the expansion and acquires a reception signal. By mathematically analyzing the reception signal, a sound pressure distribution of the photoacoustic wave generated by the photoacoustic effect in the inspection object can be imaged (hereinafter, referred to as photoacoustic wave image). Based on the photoacoustic wave image acquired as described above, an optical characteristic distribution, or more particularly a light absorption coefficient distribution of the inside of the inspection object can be acquired. These pieces of information can be used for quantitative measurement for a specific substance in the inspection object, for example, glucose or hemoglobin, contained in the blood.
Also, it is desirable to improve resolution for imaging a finer light absorber by using the photoacoustic effect. To improve the resolution, there is promoted development of a photoacoustic microscope with resolution of photoacoustic imaging improved by converging sound and collecting pulsed light.
NPL 1 suggests an ultrasonic focus photoacoustic microscope that can image an image of a blood vessel present in a region near the skin with high resolution by using an acoustic lens.
In vivo dark-field reflection-mode photoacoustic microscopy, Vol. 30, No. 6, OPTICS LETTERS
In the photoacoustic microscope, it is important to recognize the measurement position on the surface of a living body. However, in NPL 1, since an ultrasonic detecting element and an optical system are arranged above the living body, it is difficult to observe the surface of the living body by using a camera. Also, for example, if an inspection object is measured in a wider range, it has been difficult to correctly recognize the measurement position in the measurement range.
The present invention is made in light of the above-described situations, and the present invention provides an inspection object information acquiring apparatus that can correctly recognize the measurement position on a surface of an inspection object in a wide range.
Accordingly, the present invention provides an inspection object information acquiring apparatus including a light source; an optical element configured to collect light emitted from the light source; an acoustic wave detecting element configured to detect an acoustic wave, which is generated when an inspection object is irradiated with the light collected by the optical element, and output an electrical signal; an acoustic lens located between a receiving surface for the acoustic wave of the acoustic wave detecting element and the inspection object; a signal processing unit configured to acquire information on the inspection object from the electrical signal; an image pickup unit configured to capture an image of the inspection object; and a scanning unit configured to cause the acoustic wave detecting element and the image pickup unit to scan the inspection object. The scanning unit causes the acoustic wave detecting element and the image pickup unit to scan the inspection object while holding a positional relationship between the acoustic wave detecting element and the image pickup unit.
With the aspect of the invention, the measurement position of the inspection object can be correctly recognized in the wide range.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Fig. 1 is a schematic view of a first embodiment. Fig. 2 is an illustration explaining a measurement flow of the first embodiment. Fig. 3 is a schematic view of a second embodiment. Fig. 4A illustrates a relationship between acquired images and displayed images of the second embodiment. Fig. 4B illustrates the relationship between the acquired images and the displayed images of the second embodiment. Fig. 5 is an illustration explaining a measurement flow of the second embodiment. Fig. 6 is a schematic view of a third embodiment. Fig. 7 illustrates a relationship of a position indication mark of a displayed image of the third embodiment. Fig. 8 is an illustration explaining a measurement flow of the third embodiment.
An inspection object information acquiring apparatus according to an embodiment of the present invention is briefly described with reference to Fig. 1, and then respective embodiments are described below.
As shown in Fig. 1, the inspection object information acquiring apparatus according to the embodiment of the invention includes a light source 100, and a truncated conical mirror 109 being an optical element configured to collect light emitted from the light source 100. The apparatus further includes an acoustic wave detecting element 113 configured to detect an acoustic wave, which is generated when an inspection object 133 is irradiated with the light collected by the truncated conical mirror 109 being the optical element, and output an electrical signal. The apparatus also includes an acoustic lens 115 located between a receiving surface 114 of the acoustic wave detecting element 113 and the inspection object 133. The apparatus also includes a signal processing unit 126 configured to acquire information on the inspection object 133 from the electrical signal output from the acoustic wave detecting element 113. The apparatus also includes an observation camera 117 being an image pickup unit configured to capture an image of a surface of the inspection object 133. The apparatus further includes an X-axis stage 121 and a Y-axis stage 123 being scanning units configured to cause the acoustic wave detecting element 113 and the observation camera 117 being the image pickup unit to scan the inspection object 133. The scanning units cause the acoustic wave detecting element 113 and the observation camera 117 being the image pickup unit to scan the inspection object 133 while holding the positional relationship between the acoustic wave detecting element 113 and the observation camera 117 being the image pickup unit. Accordingly, a measurement position of the inspection object can be correctly recognized in a wide range. This configuration is described below.
In an inspection object information acquiring apparatus that uses a photoacoustic effect, such as a photoacoustic microscope, when a photoacoustic wave is received, it is important to recognize the measurement position on a surface of an inspection object. Owing to this, there is an idea of providing an image pickup unit, such as a camera, in the inspection object information acquiring apparatus to recognize the measurement position of the inspection object. However, for example, if the acoustic wave detecting element scans the inspection object to measure the inspection object in a wide rage in the inspection object information acquiring apparatus, since the positional relationship between the inspection object and the acoustic wave detecting element is changed with time, it is difficult to correctly recognize the measurement position of the inspection object.
In contrast, with the embodiment of the present invention, by causing the acoustic wave detecting element 113 and the observation camera 117 being the image pickup unit to execute scanning while holding the mutual positional relationship, the measurement position can be more correctly recognized on the basis of the previously determined distance between the acoustic wave detecting element 113 and the observation camera 117.
Further, with the configuration of the embodiment of the invention, even if the inspection object 133 has a surface shape with protrusions and depressions, information in the depth direction can be easily acquired, and hence information on the surface of the inspection object can be stereoscopically recognized.
The respective configurations and other configurations (desirable additional configurations) are described below.
Light Source
The wavelength of the light source to be used in the embodiment of the invention is desirably a wavelength with which light propagates to the inside of an inspection object. If the inspection object is a living body, the light source emits light with a wavelength with which the light is absorbed by a specific component among components configuring the living body. To be specific, if the inspection object is a living body, a desirable wavelength is in a range from 500 nm to 1200 nm. To efficiently generate a photoacoustic wave, the light can be pulsed light, and the pulse width is preferably in a range from several nanoseconds to about 100 nanoseconds. The light source may use a laser, a light-emitting diode, or a flash lamp. The laser can use any of various lasers including a solid-state laser, a gas laser, a dye laser, and a semiconductor laser.
Light Transmitting Unit
The light emitted from the light source is desirably transmitted by a light transmitting unit and emitted on the inspection object. The light transmitting unit desirably uses a multimode optical fiber.
Irradiation Optical System
An irradiation optical system, including the above-described truncated conical mirror, irradiates the inspection object, such as a living body, with the light transmitted by the light transmitting unit. The irradiation optical system is configured of a collimate lens, a conical lens, and the truncated conical mirror being the above-described optical element, and is arranged so that the optical path of the irradiation optical system does not interfere with the acoustic wave detecting element or the observation camera. In this embodiment, the truncated conical mirror has a hollow structure in which a center portion is hollowed in a cylindrical shape so that the acoustic wave detecting element can be arranged.
Acoustic Wave Detecting Element
The acoustic wave detecting element receives a photoacoustic wave generated at the surface of the inspection object and in the inspection object due to the emitted pulsed light, and converts the photoacoustic wave into an electrical signal (a reception signal) being an analog signal. Any acoustic wave detecting element may be used as long as the unit can detect an acoustic wave signal. For example, a unit using a piezoelectric phenomenon, a unit using an optical resonance, or a unit using a change in capacitance may be used. Further, the acoustic lens is provided so as to selectively receive an acoustic wave from a desirable focal point. In the embodiment in Fig. 1, since the receiving surface 114 for the acoustic wave is a flat surface, the normal-line direction is uniquely determined. However, if the receiving surface for the acoustic wave is not a flat surface, for example, if the surface is a curved surface, a synthetic vector, which is acquired by drawing normal lines from respective points (representative several discrete points) of the curved surface and adding the normal lines together as a vector, may serve as the normal line. In this case, if the receiving surface is hemispherical, the synthetic vector is equivalent to the normal line extending from the center of the hemisphere.
Observation Camera
The observation camera is an image pickup unit and optically observes the surface of the inspection object. A captured camera image (a visible light image) that is captured is displayed on a monitor 163 being a display unit, and hence a measurement portion is easily selected. An object plane of the observation camera being the image pickup unit and a focal position of the acoustic wave detecting element are desirably aligned with each other in the Z direction or separated from each other by a predetermined distance. For example, to acquire information on a portion near the surface of the inspection object, adjustment may be made such that the focal position of the acoustic wave detecting element is aligned with the object plane of the observation camera. To acquire information on a deeper portion than the surface of the inspection object, adjustment may be made such that the focal position of the acoustic wave detecting element is located at a deeper side (in Fig. 1, at the negative side in the Z direction) with respect to the object plane of the observation camera. As shown in Fig. 1, an optical axis 157 of the observation camera 117 being the image pickup unit represents an image pickup direction.
Observation-Camera Illumination System
To capture an image of the inspection object more sharply, the image is desirably captured with illumination with illumination light. White illumination may be used for capturing a natural image to determine an image capturing position. However, illumination light of a single color may be used depending on the purpose of use. Also, illumination light other than visual light, such as ultraviolet light or infrared light, may be used depending on the purpose of use as long as the sensitivity of the observation camera is ensured.
The illumination light desirably uniformly illuminates the inspection object. However, light with a known geometric light and dark pattern, such as a mesh pattern, may be emitted for image analysis (described later).
Housing
A housing also serves as a supporting unit configured to support the acoustic wave detecting element and the observation camera being the image pickup unit. The acoustic wave detecting element and the observation camera are fixed with a predetermined gap in the X direction. To be specific, as shown in Fig. 1, the acoustic wave detecting element 113 and the observation camera 117 being the image pickup unit are integrally supported by the housing. Further, in this embodiment, the housing being the supporting unit as shown in Fig. 1 supports the acoustic wave detecting element and the image pickup unit so that a normal-line direction 150 of the receiving surface 114 of the acoustic wave detecting element 113 and the optical axis 157 of the observation camera 117 being the image pickup unit are substantially parallel to each other. Accordingly, the axis during image capturing of an inspection object image acquired by the observation camera is aligned with the axis during image capturing of an inspection object information image acquired by the acoustic wave detecting element and a signal processing unit (described later). Hence a distortion is hardly generated between these images. In this embodiment, the illumination optical system is also supported by the supporting unit. Since a housing 101 being the supporting unit integrally supports the acoustic wave detecting element 113 and the observation camera 117 being the image pickup unit, the positional relationship between the acoustic wave detecting element 113 and the observation camera 117 being the image pickup unit is easily held during scanning.
Scanning Unit
As described above, the scanning unit includes the X-axis stage 121 and the Y-axis stage 123, and causes the acoustic wave detecting element 113 and the observation camera 117 to scan the inspection object 133 while holding the positional relationship between the acoustic wave detecting element 113 and the observation camera 117. In this embodiment, as described above, since the acoustic wave detecting element 113 and the observation camera 117 are supported by the housing 101 being the supporting unit, the housing 101 being the supporting unit executes scanning one-dimensionally, two-dimensionally, or three-dimensionally along the inspection object 133. Although described later, the scanning direction of the acoustic wave detecting element 113 and the observation camera 117 being the image pickup unit with respect to the inspection object 133 may be a direction from the acoustic wave detecting element 113 to the image pickup unit (in Fig. 1, the positive X direction). Accordingly, although described later, the positional alignment between the inspection object image acquired by the observation camera 117 and the acoustic wave detecting element is easily executed.
Signal Collecting Unit
A signal collecting unit collects the electrical signal acquired by the acoustic wave detecting element. For efficient processing, the signal collecting unit desirably includes an A/D converter that converts an analog signal into a digital signal.
Signal Processing Unit
The signal processing unit generates a two-dimensional or three-dimensional photoacoustic wave image or an optical characteristic distribution of the inside of the inspection object from the electrical signal collected by the signal collecting unit.
The photoacoustic wave image can be generated by detecting the electrical signal by envelope detection and replacing a signal value per time into a signal value in the depth direction of the inspection object.
Image Recording Unit
An image recording unit records the inspection object image information acquired by the observation camera. The inspection object image information recorded in the recording unit may be in any of various forms, such as still image information, continuous image information on still images during scanning, and movie information during scanning.
Image processing unit
An image processing unit generates an image to be displayed on the display unit. The image processing unit causes the display unit to display the inspection object information acquired by the signal processing unit and the inspection object image information captured by the observation camera 117 being the image pickup unit. The positional relationship between the acoustic wave detecting element and the observation camera is previously determined. Hence, an image corresponding to the position of the acoustic wave detecting element can be displayed by displaying recorded continuous images with a temporal delay. That is, if the scanning direction is from the acoustic wave detecting element to the image pickup unit, since the positional relationship between the acoustic wave detecting element and the observation camera is previously determined, the inspection object image information relating to a portion of the inspection object located in front of the acoustic wave detecting element can be displayed on the display unit, from among the inspection object image information recorded in the recording unit, during scanning of the acoustic wave detecting element and the image pickup unit on the inspection object. Also, the still image information on the inspection object recorded in the recording unit and a position indication mark indicative of the position of the acoustic wave detecting element during scanning may be displayed in a superposed manner.
Also, the observation camera can acquire inspection object image information at a plurality of different positions. With this method, information in the depth direction can be acquired by using a known calculation method of stereoscopy based on the principle of triangulation from images acquired at two different positions. That is, the stereoscopic shape of the inspection object can be calculated and acquired. To be specific, the stereoscopic shape of the inspection object can be calculated on the basis of a plural pieces of inspection object image information relating to different portions of the inspection object recorded in the recording unit. It is known that the stereoscopy provides a higher precision as the number of viewpoints to be used for calculation is larger. However, as described above, since the observation camera can acquire an image at a desirable position, highly precise three-dimensional shape data (stereoscopic shape data) can be acquired.
When the three-dimensional shape data is generated, by executing calculation with the image processing unit by using a geometric pattern such as the mesh pattern for the illumination light as described above, the triangulation is easily executed and hence the precision of the three-dimensional shape data can be improved. In this embodiment, the stereoscopic shape of the inspection object is acquired by the image processing unit. However, it is not limited thereto. In addition to the image processing unit, a stereoscopic shape acquiring unit configured to calculate the stereoscopic shape of the inspection object may be provided. Also, in this case, the scanning unit may cause the acoustic wave detecting element 113 and the observation camera 117 to scan the inspection object while changing the position of the acoustic wave detecting element 113 in a focal length direction based on information on the stereoscopic shape of the inspection object acquired by the stereoscopic shape acquiring unit. Accordingly, for example, the surface of the surface can be more correctly measured.
Display Unit
As described above, the display unit displays the information on the inspection object acquired by the signal processing unit and the information on the inspection object image captured by the observation camera 117 being the image pickup unit.
The display unit may use a typical flat-screen display element. Also, a known three-dimensional display element for displaying the above-described stereoscopic image may be used.
Scanning-range Input Unit
A scanning-range input unit is configured to input a scanning range of the acoustic wave detecting element 113 and the observation camera 117 being the image pickup unit by the scanning unit for the inspection object 133. To be specific, the scanning-range input unit inputs a scanning range based on the image of the observation camera displayed on the display unit. Actual scanning is executed with regard to the distance between the acoustic wave detecting element and the observation camera.
Scanning Control Unit
A scanning control unit controls a mechanical scanning range in a horizontal plane for the inspection object according to the scanning-range input unit. A mechanism configured to adjust the distance between the housing and the inspection object to a proper distance in accordance with the information on the above-described three-dimensional shape (stereoscopic shape) may be further provided.
The above-described configuration is a configuration desirable for the inspection object information acquiring apparatus according to this embodiment of the invention.
More specific configurations are described in the following embodiments.
First Embodiment
Fig. 1 is a conceptual diagram explaining a first embodiment of an inspection object information acquiring apparatus of the invention. In the drawing, reference sign 100 denotes a pulse light source configured of an optical parametric oscillator (OPO) laser that generates pulsed light with a wavelength of 800 nm, a pulse width of 5 nsec, and a repetition frequency of 100 Hz. Reference sign 103 denotes an optical fiber. The optical fiber 103 functions as the light transmitting unit. Reference sign 105 denotes a condenser lens, 107 denotes a conical lens, and 109 denotes a truncated conical mirror configuring an irradiation optical system. Reference sign 111 denotes light emitted from the optical fiber 103. Respective components of the irradiation optical system are arranged so that the light 111 passes through the irradiation optical system and is collected at a desirable position. Reference sign 113 denotes an acoustic wave detecting element using lead zirconate titanate (PZT) as a piezoelectric material and having a center frequency of 50 Hz, and 115 denotes an acoustic lens provided at a distal end of the acoustic wave detecting element 113.
Reference sign 117 denotes an observation camera 117, and 119 denotes an image forming lens provided at a distal end of the observation camera 117.
Reference sign 101 denotes a housing. The housing 101 integrally supports the irradiation optical system, the acoustic wave detecting element 113, and the observation camera 117. The housing 101 is connected to an X-axis stage 121 and a Y-axis stage 123 through a support arm 125. Also, the X-axis stage 121 and the Y-axis stage 123 are electrically connected to a scanning control unit 127, and can cause the housing 101 to execute scanning. As described above, in the state in which the housing being the supporting unit integrally supports the acoustic wave detecting element 113 and the observation camera 117, by causing the housing to scan an inspection object 133, scanning is executed while the positional relationship between the acoustic wave detecting element 113 and the observation camera 117 is held.
Reference sign 133 denotes the inspection object. The inspection object 133 is placed on a support table 131. Although not illustrated, the inspection object 133 and the support table 131 are movable in the Z direction.
Reference sign 153 denotes side walls, and 151 denotes a thin film. A water tank surrounded by the side walls 153 and the thin film 151 is filled with water 155. The thin film 151 is configured of a material that transmits light and ultrasound.
A photoacoustic wave (not indicated in the drawing) generated from the inspection object 133 as the result of the irradiation with the light 111 propagates through the thin film 151 and the water 155, and reaches the acoustic wave detecting element 113 through the acoustic lens 115. The acoustic wave detecting element 113 receives the photoacoustic wave and converts the photoacoustic wave into an electrical signal being an analog signal. By the effect of the acoustic lens 115, the photoacoustic wave generated from the focal position can be selectively received. Hence, the position in the Z direction of the inspection object 133 is adjusted so that an observation subject portion of the inspection object 133 is located near the focal point. This adjustment may be made so that the focal point of the acoustic wave detecting element is located on a plane extending from the object plane of the observation camera 117 being the image pickup unit or located at a position separated from the plane extending from the object plane of the observation camera 117 by a predetermined distance. In general, the object plane of an observation camera (the focal point plane of an observation camera) can be aligned with a surface of an inspection object. In other words, the above-described positional arrangement may be that the focal point of the acoustic wave detecting element is located at the surface of the inspection object, or located at a position separated from the surface of the inspection object by a predetermined distance (the inside of the inspection object).
The received electrical signal is collected by a signal collecting unit (not indicated in the drawing).
The acoustic wave detecting element 113 executes one-dimensional or two-dimensional scanning, and executes the irradiation with light and the collection of signals in synchronization with the scanning of the acoustic wave detecting element 113. Then, a signal processing unit 126 generates a two-dimensional or three-dimensional photoacoustic wave image of the inside of the inspection object from the collected electrical signal.
The image forming lens 119 provided at the distal end of the observation camera 117 includes an air region therein, and is arranged so that the outside of the image forming lens 119 is dipped in the water 155. The positions of the observation camera 117 and the image forming lens 119 are adjusted so that the image of the surface of the inspection object 133 is formed on an image pickup element of the camera through the water 155.
Reference sign 161 denotes an image storage unit. The image storage unit 161 stores the image acquired by the observation camera 117, and further displays the image on the monitor 163. Reference sign 165 denotes a scanning-range input unit 165. The scanning-range input unit 165 inputs a scanning range of the acoustic wave detecting element determined on the basis of the image of the observation camera 117 displayed on the monitor 163. The scanning control unit 127 controls the housing 101 based on the input scanning range.
A flow when measurement is actually executed is described with reference to Fig. 2.
Step S1001
An image of an inspection object acquired by the observation camera 117 is displayed on the monitor 163.
Step S1002
A measurement position and a measurement range are determined.
Step S1003
The measurement position and the measurement range are input by the input unit 165.
Step S1004
The acoustic wave detecting element 113 is moved to a desirable position based on the input measurement position and measurement range. At this time, while the distance between the acoustic wave detecting element 113 and the observation camera 117 is held, the position on the acquired image and the position of the acoustic wave detecting element 113 are aligned with regard to the distance between the acoustic wave detecting element 113 and the observation camera 117.
Step S1005
A photoacoustic wave is received, and the photoacoustic wave is converted into an electrical signal.
Step S1006
The electrical signal is collected.
Step S1007
It is determined whether scanning is ended or not. If scanning is not ended, the acoustic wave detecting element 113 is moved to a desirable position, and Step S1005 and Step S1006 are repeated.
Step S1008
A photoacoustic wave image of the inside of the inspection object is generated.
As described above, with this embodiment, the surface of the inspection object can be observed in a wide range, and the position of the photoacoustic wave detecting element can be easily figured out from the image of the surface of the inspection object. Accordingly, the measurement position can be more correctly recognized. That is, since the acoustic wave detecting element and the observation camera scan the inspection object while the positional relationship between the acoustic wave detecting element and the observation camera is held, measurement with the acoustic wave detecting element at a portion constantly separated from the center of the image of the surface of the inspection object by a predetermined distance can be recognized. It is desirable to display a scale on the image of the surface of the inspection object so that the measurement position can be more correctly recognized.
Second Embodiment
A second embodiment of the invention is described with reference to Fig. 3. In the drawing, the same number is applied to the same portion as that in Fig. 1, and the description thereof is omitted. The difference from the first embodiment is that an image by the observation camera acquired at the same position as the measurement position of the acoustic wave detecting element is displayed on the monitor during scanning.
In Fig. 3, reference sign 201 denotes an image recording unit. The image recording unit 201 has a function of continuously recording images (a movie) acquired by the observation camera 117. Reference sign 203 denotes an image processing unit. The image processing unit 203 has a function of acquiring positional information of the acoustic wave detecting element 113 from a scanning control unit 227, selecting an image in the case in which the observation camera 117 is located at the position from the image recording unit 201, and displaying the image on the monitor 163.
The distance between the acoustic wave detecting element 113 and the observation camera 117 is previously determined. If the housing 101 scans at a constant speed in a direction from the acoustic wave detecting element 113 to the observation camera 117 (the positive X direction in Fig. 3), first, the observation camera 117 passes through a certain point of the inspection object 133, and then the acoustic wave detecting element 113 passes through the same point with a delay of a constant time. Accordingly, by continuously recording the images by the observation camera 117 and displaying the images on the monitor 163 with the delay of the constant time, the image on the monitor and the acquired inspection object information apparently correspond to each other.
This state is described with reference to Figs. 4A and 4B. Fig. 4A illustrates a series of images acquired by the observation camera 117 when scanning is provided in the positive X direction. Fig. 4B illustrates a series of images displayed on the monitor 163.
Before measurement with the acoustic wave detecting element 113 is started, acquisition of an image by the observation camera 117 is started. This time is determined depending on the distance between the acoustic wave detecting element 113 and the observation camera 117, and the scanning speed. In the drawings, three images are acquired before start of measurement. Then, images are displayed on the monitor 163 at a timing when the acoustic wave detecting element 113 enters a measurement range. At this time, if an image being three images before is displayed, the measurement position corresponds to the display image on the monitor. Fig. 3 illustrates the case on one-dimensional (X direction) scanning. If two-dimensional scanning is executed, scanning is provided in the positive X direction first, then, movement is provided in the Y direction by a predetermined distance, the X position is returned to the start position, and then scanning may be provided in the position X direction again.
A flow when measurement is actually executed is described with reference to Fig. 5.
Step S2001
An image acquired by the observation camera 117 is displayed on the monitor 163.
Step S2002
A measurement position and a measurement range are determined.
Step S2003
The measurement position and the measurement range are input by the input unit 165.
Step S2004
The acoustic wave detecting element 113 is moved to a desirable position based on the input measurement position and measurement range. At this time, the distance between the acoustic wave detecting element 113 and the observation camera 117 is considered so that the observation camera 117 can acquire an image in a measurement range of an actual inspection object.
Step S2005
The acoustic wave detecting element 113 scans at a constant speed.
Step S2006
Acquisition of an image is started when the observation camera 117 enters the measurement range.
Step S2007
Reception of a photoacoustic wave and conversion of the photoacoustic wave into an electrical signal are started when the acoustic wave detecting element 113 enters the measurement range.
Step S2008
An image corresponding to the position of the acoustic wave detecting element 113 is displayed on the monitor 163.
Step S2009
The electrical signal is collected.
Step S2010
It is determined whether scanning is ended or not. If scanning is not ended, the acoustic wave detecting element 113 is moved to a desirable position, and Step S2005 to Step S2009 are repeated.
Step S2011
A photoacoustic wave image of the inside of the inspection object is generated.
As described above, with this embodiment, since the image of the surface of the inspection object displayed on the monitor corresponds to the position of the inspection object information acquired by the acoustic wave detecting element, the measurement position can be more correctly recognized. For example, if the monitor 163 is observed while the inspection object information acquired by the acoustic wave detecting element 113 is displayed on an oscilloscope, for example, it can be visually recognized that the signal intensity increases when the acoustic wave detecting element 113 approaches an absorber. Accordingly, the measurement position can be more correctly recognized.
Third Embodiment
A third embodiment of the invention is described with reference to Fig. 6. In the drawing, the same number is applied to the same portion as that in Fig. 1, and the description thereof is omitted. The difference from the first embodiment is that a position indication mark indicative of the measurement position by the acoustic wave detecting element is superposed on an image by the observation camera, and the position indication mark and the image are displayed on the monitor during scanning. The second embodiment is effective if the measurement range is larger than the range of the image on the monitor. In other words, if the range of the image on the monitor is larger than the measurement range, it is not meaningful that the image is displayed while being moved depending on the position of the acoustic wave detecting element. This embodiment is effective in such a case.
In Fig. 6, reference sign 301 denotes an image processing unit. The image processing unit 301 has a function of acquiring positional information of the acoustic wave detecting element 113 from the scanning control unit 227, superposing a position indication mark indicative of the measurement position by the acoustic wave detecting element on an image recorded in the image storage unit 161, and displaying the image on the monitor 163.
This state is described with reference to Fig. 7. In the drawing, reference sign 303 denotes an image recorded in the image storage unit 161. Also, reference sign 305 denotes a position indication mark generated on the basis of the positional information of the acoustic wave detecting element 113 from the scanning control unit 227, and indicates the measurement position by the acoustic wave detecting element. Reference sign 307 denotes an arrow indicative of the state of movement of the position indication mark 305. The arrow 307 is not actually displayed on the monitor. The image 303 and the position indication mark 305 are displayed on the monitor 163 in a superposed manner.
A flow when measurement is actually executed is described with reference to Fig. 8.
Step S3001
An image acquired by the observation camera 117 is displayed on the monitor 163.
Step S3002
A measurement position and a measurement range are determined.
Step S3003
The measurement position and the measurement range are input by the input unit 165.
Step S3004
The acoustic wave detecting element 113 is moved to a desirable position based on the input measurement position and measurement range. At this time, the position on the acquired image and the position of the acoustic wave detecting element 113 are aligned with regard to the distance between the acoustic wave detecting element 113 and the observation camera 117.
Step S3005
The acoustic wave detecting element 113 scans at a constant speed.
Step S3006
Reception of a photoacoustic wave and conversion of the photoacoustic wave into an electrical signal are started.
Step S3007
A position indication mark indicative of the position of the acoustic wave detecting element 113 is superposed on the image displayed in Step S3001 and displays the position indication mark and the image on the monitor 163.
Step S3008
The electrical signal is collected.
Step S3009
It is determined whether scanning is ended or not. If scanning is not ended, the acoustic wave detecting element 113 is moved to a desirable position, and Step S3005 to Step S3008 are repeated.
Step S3010
A photoacoustic wave image of the inside of the inspection object is generated.
As described above, with this embodiment, since the positional information of the acoustic wave detecting element is displayed on the image of the surface of the inspection object displayed on the monitor, the measurement position can be more correctly recognized.
Fourth Embodiment
A fourth embodiment of the invention is described with reference to Fig. 6. The difference from the first to third embodiments is that information in the depth direction with respect to the camera is acquired by using image information of the observation camera at a plurality of positions.
As described above, if images are acquired at a plurality of positions, information in the depth direction can be acquired by calculation. In this embodiment, a flow (not shown) when measurement is actually executed is described as follows.
Step S4001
The observation camera 117 scans, and acquires images at two or more different positions.
Step S4002
A three-dimensional shape (a stereoscopic shape) of a surface of an inspection object is acquired by calculation.
Step S4003
A projection image from the front is displayed on the monitor 163.
Step S4004
A measurement position and a measurement range are determined.
Step S4005
The measurement position and the measurement range are input by the input unit 165.
Step S4006
The acoustic wave detecting element 113 is moved to a desirable position based on the input measurement position and measurement range. At this time, the position on the acquired image and the position of the acoustic wave detecting element 113 are aligned with regard to the distance between the acoustic wave detecting element 113 and the observation camera 117.
Step S4007
The acoustic wave detecting element 113 scans. At this time, based on the information in the depth direction acquired by calculation, scanning is provided while the constant distance is held between the acoustic wave detecting element and the inspection object. In other words, by changing the position of the acoustic wave detecting element in the focal point direction, scanning is provided while the constant distance is held between the acoustic wave detecting element and the inspection object.
Step S4008
Reception of a photoacoustic wave and conversion of the photoacoustic wave into an electrical signal are started.
Step S4009
The electrical signal is collected.
Step S4010
It is determined whether scanning is ended or not. If scanning is not ended, the acoustic wave detecting element 113 is moved to a desirable position, and Step S4007 to Step S4009 are repeated.
Step S4011
A photoacoustic wave image of the inside of the inspection object is generated.
As described above, since the constant distance is held between the inspection object and the acoustic wave detecting element, a sample is constantly held within a depth of field. A sharp image can be acquired. To be specific, if a sample located to extend along the surface shape of an inspection object, for example, a blood vessel or the like extending in parallel to the skin surface is measured, for the surface with protrusions and depressions of the inspection object (or a portion near the surface of the inspection object), the focal point of the acoustic wave detecting element can be constantly set at the surface of the inspection object. More correct measurement can be realized.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2014-242449, filed November 28, 2014, which is hereby incorporated by reference herein in its entirety.

Claims (15)

  1. An inspection object information acquiring apparatus comprising:
    a light source;
    an optical element configured to collect light emitted from the light source;
    an acoustic wave detecting element configured to detect an acoustic wave, which is generated when an inspection object is irradiated with the light collected by the optical element, and output an electrical signal;
    an acoustic lens located between a receiving surface for the acoustic wave of the acoustic wave detecting element and the inspection object;
    a signal processing unit configured to acquire information on the inspection object from the electrical signal;
    an image pickup unit configured to capture an image of the inspection object; and
    a scanning unit configured to cause the acoustic wave detecting element and the image pickup unit to scan the inspection object,
    wherein the scanning unit causes the acoustic wave detecting element and the image pickup unit to scan the inspection object while holding a positional relationship between the acoustic wave detecting element and the image pickup unit.
  2. The inspection object information acquiring apparatus according to Claim 1, further comprising an image processing unit configured to cause a display unit to display the information on the inspection object acquired by the signal processing unit and information on the image of the inspection object captured by the image pickup unit.
  3. The inspection object information acquiring apparatus according to Claim 1 or 2, further comprising a supporting unit configured to support the acoustic wave detecting element and the image pickup unit.
  4. The inspection object information acquiring apparatus according to Claim 3, wherein the supporting unit supports the acoustic wave detecting element and the image pickup unit so that a normal-line direction of the receiving surface of the acoustic wave detecting element is substantially parallel to an optical axis of the image pickup unit.
  5. The inspection object information acquiring apparatus according to Claim 3 or 4, wherein the supporting unit integrally supports the acoustic wave detecting element and the image pickup unit.
  6. The inspection object information acquiring apparatus according to Claim 5, wherein the scanning unit causes the acoustic wave detecting element and the image pickup unit to scan the inspection object by causing the supporting unit to scan the inspection object.
  7. The inspection object information acquiring apparatus according to any one of Claims 1 to 6, wherein a focal point of the acoustic wave detecting element is located on a plane extending from an object plane of the image pickup unit.
  8. The inspection object information acquiring apparatus according to any one of Claims 1 to 6, wherein a focal point of the acoustic wave detecting element is located at a position separated from a plane extending from an object plane of the image pickup unit by a predetermined distance.
  9. The inspection object information acquiring apparatus according to any one of Claims 1 to 8, further comprising a scanning-range input unit configured to input a range of the scanning on the inspection object with the acoustic wave detecting element and the image pickup unit by the scanning unit.
  10. The inspection object information acquiring apparatus according to any one of Claims 1 to 9, further comprising a recording unit configured to record the information on the image of the inspection object acquired by the image pickup unit.
  11. The inspection object information acquiring apparatus according to any one of Claims 1 to 10, wherein a direction of the scanning on the inspection object with the acoustic wave detecting element and the image pickup unit by the scanning unit is a direction from the acoustic wave detecting element to the image pickup unit.
  12. The inspection object information acquiring apparatus according to Claim 10,
    wherein a direction of the scanning on the inspection object with the acoustic wave detecting element and the image pickup unit by the scanning unit is a direction from the acoustic wave detecting element to the image pickup unit, and
    wherein the image processing unit causes the display unit to display information on an image of the inspection object relating to a portion of the inspection object located in front of the acoustic wave detecting element, from among the information on the image of the inspection object recorded in the recording unit, while the scanning unit causes the acoustic wave detecting element and the image pickup unit to scan the inspection object.
  13. The inspection object information acquiring apparatus according to Claim 10,
    wherein the information on the image of the inspection object recorded in the recording unit is still image information, and
    wherein the image processing unit causes the display unit to display the still image information and a position indication mark indicative of a position of the acoustic wave detecting element during the scanning in a superposed manner.
  14. The inspection object information acquiring apparatus according to Claim 10, further comprising:
    a stereoscopic shape acquiring unit configured to calculate a stereoscopic shape of the inspection object,
    wherein the stereoscopic shape acquiring unit calculates the stereoscopic shape of the inspection object based on information on a plurality of images of the inspection object relating to different portions of the inspection object recorded in the recording unit.
  15. The inspection object information acquiring apparatus according to Claim 14, wherein the scanning unit causes the acoustic wave detecting element and the image pickup unit to scan the inspection object while changing a position of the acoustic wave detecting element in a focal length direction, based on information on the stereoscopic shape of the inspection object acquired by the stereoscopic shape acquiring unit.
PCT/JP2015/005598 2014-11-28 2015-11-09 Inspection object information acquiring apparatus WO2016084318A1 (en)

Applications Claiming Priority (2)

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JP2014-242449 2014-11-28
JP2014242449A JP6512801B2 (en) 2014-11-28 2014-11-28 Object information acquisition device

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