JP2009131684A - Optoacoustic signal detecting head and detecting device equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect a light absorber in the tissue with high sensitivity and resolution in a short period of time. <P>SOLUTION: An optoacoustic signal detecting head is provided to include a light emitting part 9 which emits light guided from a light source toward the inside of a sample and three or more acoustic detectors 10 arranged around the light emitting member 9 to detect an acoustic signal emitted from the light absorber in the sample, wherein two acoustic detectors 10 adjacent to the first acoustic detector 10 are disposed with an interval to adjoin in the mutually crossing direction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a photoacoustic signal detection head for measuring the distribution of an absorber inside a living body, and a detection apparatus including the same.

  Photoacoustic tomography is known as a method for measuring the distribution of absorbers inside a living body. This photoacoustic tomography is a technique for obtaining a tomographic image related to light absorption information of a tissue by making light incident on a measurement object and measuring a stress wave generated by light absorption in the measurement object (for example, Patent Document 1). reference.).

  In this photoacoustic tomography, in order to generate a transient stress wave, it is necessary that the light pulse is short with respect to the velocity of the sound wave, and a short pulse laser beam is used. The light diffused by scattering in the tissue is absorbed by an absorber in the tissue and generates a pressure wave. The generated pressure wave is detected by an acoustic transducer disposed on the tissue surface. What is detected is the time, amplitude and waveform of the pressure wave. Since the time of the pressure wave corresponds to the distance from the detection and the amplitude corresponds to the absorption amount, the distribution of the absorption amount in the depth direction is thereby measured.

  By scanning the tissue surface with a detector and repeating the measurement, a tomographic image of the tissue is obtained. The contrast of the image is related to the absorption coefficient with respect to the wavelength of the irradiated light. In order to obtain a tomographic image having high resolution, it is necessary to use a detector having high directivity. Since the acoustic transducer exhibits a response characteristic sensitive to the incident angle of the sound wave, a certain degree of lateral resolution can be obtained even if it is used as it is.

  A system using a ring-type piezoelectric element has been developed for the purpose of obtaining higher resolution of several tens of μm level (for example, see Non-Patent Document 1). This ring-type detector is obtained by increasing the directivity of the detector by utilizing the interference of sound waves. That is, the signal generated from the central axis of the ring can be detected as a strong signal because the peak of amplitude reaches the entire ring at the same time, but the signal generated at a position off the central axis is canceled out. There is a possibility of interference, and the property of being detected as a weak signal is utilized.

Japanese Patent Laid-Open No. 2002-219105

Roy GM Kolkman and 3 other authors, “Photoacoustic Monitoring and Imaging of Blood Vessels in Tissue”, Proceedings of SPE SPIE), 2002, 4618, p. 76-80

  However, unlike optical coherence tomography (OCT) and confocal microscopes, photoacoustic tomography can detect information on the deep part of a living body by detecting sound waves without being affected by light scattering. It is a featured method. For this reason, in order to detect the information of the sound waves generated in the deep part of the living body with high resolution, it is necessary to provide sound wave directivity on the detector side. On the other hand, the ring-type detector has a high directivity by using the property that an acoustic signal interferes, but has the following drawbacks.

  First, as a photoacoustic signal detector, a piezoelectric element such as PVdF (polyvinylidene fluoride resin) is often used, and the piezoelectric element has sensitivity even at a high frequency of several tens of MHz. It is a transducer suitable for detecting an acoustic signal. However, the sensitivity to components incident at an angle has the property of greatly decreasing. With a normal transducer having no hole in the center, there is no problem in detecting a signal from a portion very close to the detector. However, in a ring-type detector, a signal from a portion close to the detector at the center of the ring is incident on the ring at an angle, and the sensitivity is extremely lowered. For this reason, it is difficult to measure a signal from a portion very close to the tissue.

  Second, the required depth information range and signal waveform characteristics differ depending on the object to be measured. In order to detect the signal with high sensitivity and high resolution using a ring type detector, it is necessary to use a detector having a different ring radius. Therefore, when the measurement object is different, or when the place to be measured is different, there is an inconvenience that a detector having a ring radius suitable for the measurement object or measurement place must be used.

  Thirdly, the photoacoustic tomography can be applied to a technique for finding and imaging the location of the absorber, such as detecting an affected area in a living body with a pigment or the like. Photoacoustic tomography using a ring-type detector is an excellent method capable of finding the position of an absorber existing in the deep part of a living body with high resolution. However, in a state where the detector is fixed, it is difficult to grasp the position of the absorber because only one-dimensional information can be obtained. For this reason, it is necessary to scan the detector with a dark cloud on the tissue surface, and there is a problem that it takes time to find the position.

  The present invention has been made in view of the above-described circumstances, and a photoacoustic signal detection head capable of detecting a light absorber inside a tissue with high sensitivity and high resolution within a short period of time. It aims at providing the detection apparatus provided with.

In order to achieve the above object, the present invention provides the following means.
The invention according to claim 1 is a light emitting unit that emits light guided from a light source toward the inside of the sample, and three or more that are arranged around the light emitting unit and detect an acoustic signal generated inside the sample. And a photoacoustic signal detection head arranged at a distance from each other so that two acoustic detectors adjacent to one acoustic detector are adjacent to each other in a direction intersecting each other. provide.

  According to the present invention, when the light guided from the light source is emitted from the light emitting part toward the inside of the sample, the light is absorbed by the light absorber inside the sample and emitted as an acoustic signal from the light absorber. . The acoustic signal transmitted through the inside of the sample is detected by an acoustic detector disposed on the sample surface. Since three or more acoustic detectors are arranged around the light emitting part, detection with high directivity equivalent to that of a ring-type acoustic detector is achieved by synthesizing the acoustic signals detected by each acoustic detector. Can be performed.

  In this case, since individual acoustic signals are detected in each acoustic detector, the photoacoustic detection head remains fixed by calculating the difference in measurement time between the individual acoustic signals, and is a signal source. It becomes possible to specify the direction of the light absorber inside the sample. As a result, the photoacoustic detection head can be quickly arranged at a position most suitable for the measurement of the acoustic signal from the light absorber, and detection with high sensitivity and high resolution can be performed quickly.

The invention according to claim 2 is the photoacoustic signal detection head according to claim 1, wherein the acoustic detectors are arranged on a circumference centered at one point at intervals in the circumferential direction. A signal detection head is provided.
According to the present invention, a light absorber disposed inside a sample at the center position of a circle in which a plurality of acoustic detectors are arranged can be detected with high sensitivity and high resolution in the same manner as a ring-type photodetector. Is possible.

The invention according to claim 3 provides the photoacoustic signal detection head according to claim 2, further comprising a moving mechanism that moves the acoustic detector in a direction intersecting the circumferential direction.
According to the present invention, the detection range in the depth direction of the light absorber disposed inside the sample can be changed by moving each acoustic detector in the direction intersecting the circumferential direction by the operation of the moving mechanism. Is possible.

The invention according to claim 4 is the photoacoustic signal detection head according to claim 3, wherein the acoustic detector is moved so as to increase or decrease the radius of a circle without changing the position of the center. A detection head is provided.
According to the present invention, even if a plurality of acoustic detectors are moved by the operation of the moving mechanism, the center position of the arranged circles does not change, so the photoacoustic signal detection head is moved while being fixed to the sample surface. By operating the mechanism, it is possible to adjust the sensitivity by changing the detection range in the depth direction.

According to a fifth aspect of the present invention, in the photoacoustic signal detection head according to the first aspect, three or more of the acoustic detectors are arranged on a plurality of concentric circles centered on one point with a circumferential interval. A photoacoustic signal detection head is provided.
According to this invention, by operating three or more acoustic detectors on each circumference, measurement with high sensitivity and high resolution equivalent to those of a ring-type acoustic detector can be performed. In addition, by synthesizing the signals from the acoustic detectors for each circle in which they are arranged, the depth direction is substantially the same as moving each acoustic detector in a direction intersecting the circumferential direction. It is possible to change the detection range. That is, by combining only the signals from the acoustic detectors arranged on the inner circle, it is possible to detect light absorbers arranged at relatively shallow positions with high sensitivity, and to synthesize the signals. As the circle in which the detectors are arranged is switched to the outside, the detection range that can be detected with high sensitivity can be changed in a deeper direction.

According to a sixth aspect of the present invention, in the photoacoustic signal detection head according to the first aspect, the photoacoustic signal detection includes a swinging mechanism that swings the acoustic detector about an axis arranged in a tangential direction of the circle. Provide the head.
According to the present invention, by operating the swing mechanism, the sound detector can be swung around the axis line arranged in the tangential direction of the circle in which the sound detectors are arranged. When the acoustic detector has a high sensitivity to a vertically incident acoustic signal, such as a piezoelectric element, the acoustic detector is swung and directed toward the light absorber so as to have a high sensitivity. Detection can be performed.

According to a seventh aspect of the present invention, in the photoacoustic signal detection head according to the first aspect, the acoustic detectors are spaced apart in the circumferential direction on a plurality of circumferences around a plurality of spaced points. 3 or more photoacoustic signal detection heads are provided.
According to this invention, by operating three or more acoustic detectors on each circumference, measurement with high sensitivity and high resolution equivalent to those of a ring-type acoustic detector can be performed. In addition, by switching the circle that operates the acoustic detector, the single ring-type acoustic detector can function substantially as if it was moved in the direction of circle arrangement, and the head remains fixed. The sample surface can be sequentially scanned.

  The invention according to claim 8 is the photoacoustic signal detection head according to any one of claims 1 to 7, a light source that supplies light to the light emitting portion of the photoacoustic signal detection head, and each acoustic detection Based on the comparison result of the acoustic signals output from the detector, the detection result obtained by combining the position specifying means for specifying the position of the light absorber inside the sample and the acoustic signals output from the multiple acoustic detectors An acoustic signal detection device provided with a display unit for displaying.

  According to this invention, by operating the photoacoustic signal detection head, the light emitted from the light source is irradiated toward the inside of the sample, and the acoustic signal is detected by each acoustic detector. By operating the position specifying means in this state, the acoustic signals output from the respective acoustic detectors are compared, and the position of the light absorber inside the sample is specified based on the comparison result. Then, based on the specified position of the light absorber, the acoustic detector is arranged at a position suitable for detecting the light absorber, and the acoustic signals detected by the plurality of acoustic detectors at the position are arranged. By synthesizing, the detection result with high sensitivity and high resolution can be displayed on the display unit.

  According to the photoacoustic signal detection head and the photoacoustic signal detection apparatus having the same according to the present invention, using three or more acoustic detectors that are not arranged in a straight line, high sensitivity equivalent to that of a ring-type acoustic detector and High resolution detection performance can be achieved, and by comparing the output signals from each acoustic detector individually, the direction of presence of the light absorber to be detected present in the sample can be easily identified be able to. As a result, it is possible to quickly search for the light absorber and improve the detection efficiency.

1 is a schematic diagram showing a photoacoustic signal detection apparatus according to a first embodiment of the present invention. 1 is a perspective view showing a photoacoustic signal detection head according to a first embodiment of the present invention. It is a front view which shows the structure of the front end surface of the photoacoustic signal detection head which concerns on 2nd Embodiment of this invention. It is a front view which shows the structure of the front end surface of the photoacoustic signal detection head which concerns on 3rd Embodiment of this invention. It is a front view which shows the structure of the front end surface of the photoacoustic signal detection head which concerns on 4th Embodiment of this invention. It is a longitudinal cross-sectional view which shows the part of the front end surface of the photoacoustic signal detection head of FIG. It is a front view which shows the structure of the front end surface of the photoacoustic signal detection head which concerns on 5th Embodiment of this invention.

A photoacoustic signal detection head and a photoacoustic signal detection apparatus according to an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the photoacoustic signal detection apparatus 1 according to the present embodiment includes a photoacoustic signal detection head (hereinafter referred to as a detection head) 2, a light source 3 that supplies light to the detection head 2, and A signal processing unit 4 that processes an acoustic signal detected by the detection head 2, a display 5 that displays a detection result processed by the signal processing unit 4, and a recording unit 6 that records the detection result are provided.

  As shown in FIG. 2, the detection head 2 includes a grip portion 7 that is held by a person who performs an inspection, and light is directed toward the inside of the sample A on the tip surface 8 of the grip portion 7 that is brought into contact with the surface of the sample A. And a sound detector 10 for detecting an acoustic signal emitted from the light absorber B in the sample A.

  The light emitting part 9 is constituted by an end face of an optical fiber 11 that has passed through the grip part 7. The light emitting portion 9 is disposed at a substantially central portion of the substantially circular distal end surface 8 of the grip portion 7, and the distal end surface 8 of the grip portion 7 is disposed in contact with the surface of the sample A, whereby the sample A It can be in close contact with the surface directly or indirectly through ultrasonic jelly or the like. The optical fiber 11 is, for example, a multimode fiber having a core diameter of 100 μm or more.

  The acoustic detectors 10 are, for example, PVdF piezoelectric elements. A plurality of the acoustic detectors 10 are arranged on the circumference C around the end face of the optical fiber 11, and four in the example shown in FIG. Are arranged. The acoustic detectors 10 are arranged so as to be adjacent to each other in a direction crossing each other. That is, these acoustic detectors 10 are two-dimensionally arranged. Therefore, for example, in the example shown in FIG. 2, a line connecting the first acoustic detector 10-1 and the second acoustic detector 10-2, and the second acoustic detector 10-2 and the third acoustic detector. The line connecting the detector 10-3 intersects. Or the line which connects the 1st acoustic detector 10-1 and the light emission part 9 and the line which connects the 4th acoustic detector 10-4 and the light emission part 9 cross | intersect.

  Each acoustic detector 10 is formed in a disk shape having a diameter of about 200 μm and a thickness of about 9 μm. The detection surface of each acoustic detector 10 is disposed in the same plane as the distal end surface 8 of the grip portion 7 that is brought into contact with the surface of the sample A. Each acoustic detector 10 is connected to a wiring 12 that transmits an electrical signal obtained by detecting the acoustic signal.

  The light source 3 is, for example, a Q-switched Nd: YAG laser having a second harmonic of 532 nm. The light source 3 is connected to the other end of the optical fiber 11 so that the laser beam L can be emitted from the light emitting unit 9 through the optical fiber 11.

The signal processing unit 4 is configured by a computer, for example. The signal processing unit 4 is connected to a wiring 12 drawn from the acoustic detector 10. The electric signal from each acoustic detector 10 is amplified by a preamplifier (not shown) and then individually sent to the signal processing unit 4 via each wiring 12.
The signal processing unit 4 includes a comparison unit 13, a determination unit 14, a synthesis unit 15, and an image processing unit 16. A recording unit 6 is connected to the signal processing unit 4 so that the detection result can be recorded.

The comparison unit 13 compares the magnitudes of the signals from the acoustic detectors 10 or calculates the difference. The determination unit 14 determines which acoustic detector 10 the light absorber B to be detected is closer to based on the calculation result in the comparison unit 13.
The synthesizer 15 synthesizes the output signals from the acoustic detectors 10. The recording unit 6 can store the output signal from the combining unit 15 in association with the position information of the detection head 2.

  The image processing unit 16 is configured to image the signal output from the synthesizing unit 15 or the recording unit 6 and output the image to the display 5. In addition, the image processing unit 16 indicates a moving direction of the detection head 2 for performing highly sensitive detection based on the comparison result of the output signals from the acoustic detectors 10 calculated by the comparison unit 14. Is output to the display 5.

The operation of the photoacoustic signal detection apparatus 1 according to the present embodiment configured as described above will be described below.
In order to detect the light absorber B inside the sample A using the photoacoustic signal detection apparatus 1 according to the present embodiment, the operator holds the grip part 7 of the detection head 2 and the light emitting part 9. The front end surface 8 on which the acoustic detector 10 is disposed is brought into close contact with the surface of the sample A. Ultrasonic jelly etc. are apply | coated to the surface of the sample A as needed.

  In this state, the laser light L is supplied from the light source 3 and the signal processing unit 4 and the display 5 are operated. When the laser light L is emitted from the light source 3, the laser light L reaches the light emitting part 9 through the optical fiber 11 and is emitted from the light emitting part 8 toward the inside of the sample A. When the light absorber B such as an aneurysm is present inside the sample A, the laser beam L is absorbed by the light absorber B, so that an acoustic signal is emitted from the light absorber L and the surface of the sample A It is detected by the acoustic detector 10 arranged.

  The acoustic signal detected by the acoustic detector 10 is converted into an electrical signal and synthesized by the synthesis unit 15. The synthesized electric signal is a signal obtained by interfering with the signal obtained by each acoustic detector 10. Therefore, the electrical signal output from the synthesizing unit 15 is imaged by the image processing unit 16 and viewed on the display 5, whereby a predetermined depth inside the sample A on the central axis S of the circle C where the acoustic detector 10 is disposed. The light absorber B arranged in the range can be detected with high sensitivity. In addition, by recording a plurality of synthesized electrical signals in the recording unit in association with the position of the detection head 2, the detection results at each position can be compared and viewed after the detection operation is completed.

  Furthermore, according to the photoacoustic signal detection apparatus 1 according to the present embodiment, the acoustic signals detected by the respective acoustic detectors 10 are sent to the comparison unit 13 for comparison calculation. For example, by comparing the magnitudes of electrical signals from two acoustic detectors 10 arranged at diagonal positions and adjacent positions, the determination unit 14 determines which acoustic detector 10 is based on the comparison result. Whether it is close to the light absorber B is determined. In addition, it is possible to determine which acoustic detector 10 is close to the light absorber B by comparing the magnitudes of the electrical signals from all the acoustic detectors 10.

  Then, a signal indicating an instruction as to which direction the detection head 2 can be moved to detect the light absorber B with high sensitivity is sent from the determination unit 14 to the image processing unit 16. Thus, the instruction can be displayed on the display 5.

  As a result, the inspection operator confirms the state inside the sample A displayed on the display 5 by an image and moves the detection head 2 according to the movement direction instruction of the detection head 2 supplied from the determination unit 14. Thus, the state inside the sample A can be detected with higher sensitivity.

  Thus, according to the photoacoustic signal detection apparatus 1 according to the present embodiment, the acoustic signals detected by the plurality of acoustic detectors 10 arranged on the same circumference at intervals are synthesized and displayed or recorded. Therefore, similarly to the ring-type acoustic detector, there is an effect that detection with high sensitivity and high resolution can be performed. Furthermore, since the acoustic signals detected individually in each acoustic detector 10 are compared, the direction in which the light absorber B is arranged can be specified. As a result, it is possible to quickly find the position of the detection head 2 capable of performing detection with high sensitivity and high resolution without performing dark scanning, thereby improving the efficiency of detection work.

  In the above-described embodiment, the number of the acoustic detectors 10 arranged on the distal end surface 8 of the grip portion 7 has been described as four. However, the present invention is not limited to this, and an arbitrary number of three or more acoustic detectors is used. The detector 10 can be employed. In addition, the four acoustic detectors 10 are arranged on the same circumference with the light emitting unit 9 as the center. However, the present invention is not limited to this, and the other two acoustic detectors 10 adjacent to the acoustic detector 10 are used. The acoustic detectors 10 may be arranged so as to be adjacent to each other in a direction crossing each other. That is, all the acoustic detectors 10 should not be arranged on the same straight line.

Further, the example in which the operator grips and moves the detection head 2 to scan the surface of the sample A has been described, but the detection head 2 is attached to an arbitrary moving mechanism (not shown) and automatically scanned. You may decide.
Moreover, although the single light emission part 9 has been arrange | positioned in the center of the circle | round | yen C where the some acoustic detector 10 is arrange | positioned, instead of this, the some light emission part 9 can be arrange | positioned in the circle C, Another light emitting part 9 may be arranged outside the circle C.

Next, a photoacoustic signal detection apparatus according to a second embodiment of the present invention will be described with reference to FIG.
The photoacoustic signal detection apparatus according to the present embodiment is different from the photoacoustic signal detection apparatus 1 according to the first embodiment in the detection head 20. In addition, the same code | symbol is attached | subjected to the location which shares a structure with 1st Embodiment, and description is simplified.
In the present embodiment, three detection heads 20 are arranged on the front end surface of the light emitting portion 9 and on the circumference of a circle C centered on the light emitting portion 9 with a circumferential interval. The acoustic detector 10 and a moving mechanism 21 for moving the acoustic detector 10 are provided.

  For example, as shown in FIG. 3, the moving mechanism 21 includes three linear grooves 23 that extend radially from the center of a disk-shaped base 22 that forms the distal end surface of the detection head 20, and these linear grooves 23. , And a drive mechanism for moving the sliders 24 along the linear grooves 23. The drive mechanism includes a first gear 26 that is rotatably supported around a through hole 25 that penetrates an optical fiber formed in the center of the base 22, and a drive gear 27 that meshes with the first gear 26. The motor 28 and three sets of slider crank mechanisms 29 are configured. Each slider crank mechanism 29 is rotatably attached around a pin 30 fixed to the base 22 around the first gear 26, and includes three second gears 31 that mesh with the first gear 26, A first arm 32 fixed to the second gear 31 and a pin 33 provided at the rocking end of the first arm 32 and a pin 34 fixed to the slider 24. Arm 35.

  The three acoustic detectors 10 are arranged at equal intervals on a circumference C around the light emitting portion 9 at the center of the base 22. As described above, the three slider crank mechanisms 29 for driving the acoustic detectors 10 mesh with the first gear 26 at the center of the base 22, so that they are driven in synchronization with the driving of the first gear 26. It is supposed to be made. As a result, these acoustic detectors 10 are arranged on the circumference C around the light emitting portion 9 at the center of the base 22 regardless of the position along the linear groove 23. .

The operation of the photoacoustic signal detection apparatus according to this embodiment configured as described above will be described below.
According to the photoacoustic signal detection apparatus according to the present embodiment, each acoustic detector 10 is arranged at a predetermined position of the linear groove 23, for example, at an outermost position with respect to the light emitting unit 9, and the light source 3 and the acoustic signal are detected. By operating the detector 10, an acoustic signal emitted from the light absorber B inside the sample A is detected. In this case, by synthesizing the acoustic signals obtained in each acoustic detector 10, it is possible to perform detection with high sensitivity and high resolution similar to a ring-type acoustic detector having a large radial dimension.

  Moreover, the direction in which the light absorber B exists can be determined by comparing the acoustic signals obtained in the acoustic detectors 10. Therefore, the light absorber B to be detected can be quickly found, and the detection efficiency can be improved.

  In this case, since the acoustic detectors 10 are arranged farthest apart, the synthesized signal obtained by these acoustic detectors 10 is relative to the light absorber B disposed in a relatively deep region inside the sample. High sensitivity. However, the sensitivity is low for the light absorber B arranged in a relatively shallow region.

  Therefore, the moving mechanism 21 is operated to move the acoustic detector 10 radially inward along the straight groove 23. Specifically, by operating the motor 28, the three sets of slider crank mechanisms 29 are operated. That is, the driving force is transmitted from the motor 28 to the slider 24 via the driving gear 27, the first gear 26, the second gear 31, and the two arms 32, 35, and the three sliders 24 and the three sliders 24 are attached thereto. The acoustic detectors 10 are respectively moved radially inward along the linear grooves 23.

Thereby, since the radial dimension of the circle in which the three acoustic detectors 10 are arranged is reduced, it functions in the same manner as a ring-type acoustic detector having a relatively small radial dimension, and a relatively shallow area inside the sample A. Can be detected with high sensitivity and high resolution. In this case, the center position of the circle C where the acoustic detectors 10 are arranged does not fluctuate even if the acoustic detectors 10 are arranged at any position of the linear grooves 23. Therefore, the detection head 20 using interference is used. The high directivity as a whole is guaranteed.
Therefore, by operating the moving mechanism 21 to move the position of the acoustic detector 10, detection can be performed with high sensitivity over a wide region from a relatively deep position to a relatively shallow position inside the sample A.

  In the above embodiment, three acoustic detectors 10 are used, but the present invention is not limited to this. Moreover, although the structure which has the slider crank mechanism 29 was employ | adopted as the moving mechanism 21 which moves the acoustic detector 10, it is not limited to this, Other arbitrary drive mechanisms can be employ | adopted.

Next, a photoacoustic signal detection apparatus according to a third embodiment of the present invention will be described below with reference to FIG. In addition, about the structure same as the already demonstrated structure, a common code | symbol is attached | subjected and description is simplified.
The photoacoustic signal detection apparatus according to the present embodiment includes a total of eight acoustic detectors 10, two concentric circles C ₁ and C ₂ centered on the light emitting portion 9 and four on the circumferential direction. Are arranged. A wiring 12 is connected to each acoustic detector 10 so that an electrical signal corresponding to the acoustic signal can be individually taken out from the acoustic detector 10.

Further, the combining unit 15 of the signal processing unit 4, four that are located on inner circle C ₁ and the output signal from the sound detector 10, the four, which is disposed on the outer circle C ₂ The output signal from the acoustic detector 10 can be synthesized separately. About another structure, it is the same as that of the photoacoustic signal detection apparatus 1 which concerns on 1st Embodiment.

The operation of the photoacoustic signal detection apparatus according to this embodiment configured as described above will be described below.
According to the photoacoustic signal detection device according to the present embodiment, the direction in which the light absorber B exists can be quickly detected by comparing the output signals from the acoustic detectors 10. This is the same as the photoacoustic signal detection apparatus according to the second embodiment.

In the photoacoustic signal detecting apparatus according to the present embodiment, first, combining the output signals from the four acoustic detector 10 which is arranged on the outer circle C _2. Thereby, the light absorber B arranged at a relatively deep position inside the sample A can be detected with high sensitivity. Then, to synthesize the output signal from the four acoustic detector 10 which is arranged on the inner circle C _1. Thereby, the light absorber arrange | positioned in the comparatively shallow position inside a sample can be detected with high sensitivity. Therefore, although it is stepwise, highly sensitive detection of the light absorber B can be performed over a wide range in the depth direction inside the sample A.

  According to the present embodiment, it is not necessary to provide the complicated moving mechanism 21 as in the second embodiment, and it can be manufactured at low cost. Moreover, since there are no movable parts, there are few failures and durable use is possible.

In the photoacoustic signal detection device according to the present embodiment, the acoustic detector 10 is arranged on the double concentric circles C ₁ and C ₂ , but may be arranged on three or more concentric circles. By doing in this way, it becomes possible to perform detection over a wide range in the depth direction inside the sample A.
In addition, although four acoustic detectors 10 are arranged on each of the circles C ₁ and C ₂ , three or five or more acoustic detectors 10 may be arranged instead.

Next, a photoacoustic signal detection apparatus according to the fourth embodiment of the present invention will be described with reference to FIGS.
The photoacoustic signal detection device according to the present embodiment is different from the photoacoustic signal detection device according to the second embodiment in the moving mechanism 40. In addition, the same code | symbol is attached | subjected to the structure same as the already described structure, and description is simplified.

  As shown in FIGS. 5 and 6, the moving mechanism 40 of the photoacoustic signal detection device according to the present embodiment has the center hole 42 of the disc-shaped base 41 constituting the distal end surface 8 of the grip portion. Three holding plates 44 that are swingably attached around an axis 43 arranged along the tangential direction of the hole 42 and hold the acoustic detector 10 respectively, and the holding plate 44 is pulled up with respect to the base 41. A spring 45 that biases in the direction and a pressing member 46 that presses the tip of the holding plate 44 in a direction to be pressed down by a driving source (not shown) are provided. A through hole through which the optical fiber 11 passes is provided in the center of the pressing member 46. 5 and 6 are explanatory diagrams of the principle. In practice, components are appropriately selected so as to achieve the above functions.

  The three holding plates 44 are arranged at equal intervals in the circumferential direction, and the three acoustic detectors 10 respectively attached to the three holding plates 44 are also centered on the light emitting portion 9. They are arranged at equal intervals on the circumference.

  According to the photoacoustic signal detection device according to the present embodiment configured as described above, the front end surface 8 of the detection head is in a vertically downward state, that is, in close contact with the upper surface of the sample A disposed on the lower side. In this state, by moving the pressing member 46 toward the distal end direction of the optical fiber 11, the distal end of the holding plate 44 in contact with the pressing member 46 is pushed down. As a result, the angle of the holding plate 44 and the acoustic detector 10 attached to the lower surface thereof approaches the horizontal.

  Each acoustic detector 10 is highly sensitive to acoustic signals from a predetermined area centered on the center line 10a of each acoustic detector 10, that is, in the direction in which the surfaces are facing each other. Therefore, each acoustic detector 10 changes its sensitive detection area downward as its angle approaches horizontal. On the other hand, in the case of using a synthesized signal for synthesizing output signals from the three acoustic detectors 10 arranged at equal intervals in the circumferential direction in the synthesizing unit 15, the center line 10a of each acoustic detector 10 is Sensitivity is high with respect to the acoustic signal from the predetermined area P centering on the intersecting point. Therefore, according to the photoacoustic signal detection apparatus of the present embodiment, an acoustic signal from the region P having a predetermined depth inside the sample A arranged on the central axis S of the optical fiber 11 can be detected with high sensitivity. Then, as the angles of all the acoustic detectors 10 approach the horizontal direction, the highly sensitive detection region P moves to a deep region inside the sample A along the central axis S of the optical fiber 11. .

  For example, by first pressing the pressing member 46 and pressing down the holding plate 44, the light absorber B in a deep region inside the sample A is detected with high sensitivity, and then the pressing force on the pressing member 46 is reduced. As a result, the holding plate 44 is pulled up by the spring 45. Thereby, it becomes possible to detect the light absorber B in a shallow region gradually with high sensitivity, and the light absorber B can be detected over a wide range in the depth direction.

Next, a photoacoustic signal detection apparatus according to the fifth embodiment of the present invention will be described with reference to FIG. FIG. 7 is a view of the detection head of the present embodiment as viewed from the front end surface side. In this embodiment, the same reference numerals are given to the same components as those already described to simplify the description.
As shown in FIG. 7, the photoacoustic signal detection device according to the present embodiment includes a plurality of, for example, 30 light emitting units 9 arranged in a line at intervals in one direction, and these light emitting units 9. And a plurality of, for example, six acoustic detectors 10 arranged at intervals on the circumference centered on. Two acoustic detectors 10 of the six acoustic detectors 10 arranged around the two adjacent light emitting portions 9 are shared. About another point, it is equivalent to the photoacoustic signal detection apparatus which concerns on 1st Embodiment.

According to the photoacoustic signal detection device according to the present embodiment configured as described above, the laser light L is irradiated from the light emitting units 9 toward the inside of the sample A while the detection head is in close contact with the surface of the sample A. The acoustic signals are individually detected by the acoustic detectors 10. In this case, the synthesis unit 15 of the signal processing unit 4 first synthesizes the output signals from the six acoustic detectors 10 arranged on the circle C ₁ centered on the first light emitting unit 9. Next, the output signals from the six acoustic detectors 10 arranged on the circle C ₂ centering on the second light emitting section 9 are synthesized and outputted, and thereafter, the synthesized signals are sequentially outputted in the same manner. To do.

  As a result, according to the photoacoustic signal detection device according to the present embodiment, the detection head is not moved on the surface of the sample A in the arrangement direction of the light emission units 9 but only in the direction intersecting the arrangement direction of the light emission units 9. It is possible to obtain the same effect as when the detection head 2 according to the first embodiment is scanned two-dimensionally on the surface of the sample A, and the detection efficiency can be improved.

  In the photoacoustic signal detection apparatus according to the present embodiment, the light emitting units 9 are arranged in a line in one direction, but instead, they may be arranged two-dimensionally. By doing so, it is possible to perform two-dimensional scanning of the surface of the sample A without moving the detection head at all. In this case, a plurality of acoustic detectors 10 are also arranged around the light emitting unit 9 on a plurality of concentric circles having different radii. Therefore, as in the third embodiment, the synthesis is performed. It is possible to perform highly sensitive detection over a wide range in the depth direction inside the sample A simply by selecting the signal to be performed.

  In addition, the number of acoustic detectors 10 has been reduced by sharing a part of acoustic detectors 10 arranged on two circumferences centering on the adjacent light emitting portions 9, but instead of this, You may decide to arrange | position around each light emission part 9 without making it share.

A Sample B Light absorber C, C ₁ , C ₂ , C ₃ , C ₄ , C ₅ circle L Laser light (light)
1 Photoacoustic signal detection device 2 Detection head (photoacoustic signal detection head)
3 Light source 5 Display (display unit)
9 Light emission part 10 Acoustic detector 14 Judgment part (position specifying means)
21 Moving mechanism 43 Axis 44 Holding plate (swinging mechanism)
45 Spring (swing mechanism)
46 Pressing member (swing mechanism)

Claims (4)

A light emitting unit that emits light guided from the light source toward the inside of the sample, and three or more acoustic detectors that are arranged around the light emitting unit and detect an acoustic signal generated inside the sample,
A photoacoustic signal detection head in which two acoustic detectors adjacent to one acoustic detector are spaced apart from each other so as to be adjacent to each other in a direction crossing each other.   2. The photoacoustic signal detection head according to claim 1, wherein three or more acoustic detectors are arranged on a plurality of concentric circles centered at one point with a circumferential interval.   2. The photoacoustic signal detection head according to claim 1, wherein three or more acoustic detectors are arranged at intervals in a circumferential direction on a plurality of circumferences around a plurality of spaced points. The photoacoustic signal detection head according to any one of claims 1 to 3,
A light source for supplying light to the light emitting portion of the photoacoustic signal detection head;
Based on the comparison result of the acoustic signal output from each acoustic detector, the position specifying means for specifying the position of the light absorber inside the sample,
A photoacoustic signal detection apparatus comprising: a display unit that displays a detection result obtained by synthesizing acoustic signals output from a plurality of acoustic detectors.

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