JP2019033800A - Photoacoustic probe, light source substrate, and photoacoustic device - Google Patents

Abstract

To provide a structure that efficiently drives a semiconductor light emitting element in a photoacoustic probe.SOLUTION: A photoacoustic probe has a light source substrate, and a probe for receiving an acoustic wave generated from a subject by the light emitted from the light source substrate and converting it into an electric signal. The light source substrate is characterized in that a light emitting element group 200A configured by containing multiple semiconductor light emitting elements being serially-connected is mounted in a first surface, return wiring 200BP connected to one end of the light emitting element group is mounted in a second surface being opposite to the first surface, and the potential of the return wiring is constant without depending on an electrified state of the semiconductor light emitting element.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an apparatus for acquiring information on a subject using a photoacoustic effect.

In recent years, in the medical field, research for imaging structural information in a subject and physiological information, that is, functional information has been advanced. Recently, photoacoustic tomography (PAT) has been proposed as one of such techniques.
When light such as laser light is irradiated on a living body that is a subject, an acoustic wave (typically, an ultrasonic wave) is generated when the light is absorbed by a living tissue in the subject. This phenomenon is called a photoacoustic effect, and an acoustic wave generated by the photoacoustic effect is called a photoacoustic wave. Since tissues constituting the subject have different optical energy absorption rates, the sound pressures of the generated photoacoustic waves are also different. In PAT, the generated photoacoustic wave is received by a probe, and the received signal is mathematically analyzed, whereby characteristic information in the subject can be acquired.

  In an apparatus using photoacoustic tomography, a light source that generates light to be irradiated on a subject is required. As an invention related to this, for example, Patent Document 1 discloses a light source in which a plurality of semiconductor light emitting elements are mounted on a printed circuit board and a heat dissipation mechanism is provided on the opposite surface.

JP 2017-29288 A

  When the semiconductor light emitting element and the heat dissipation mechanism are close to each other as in the light source described in Patent Document 1, a capacitor may be formed and capacitive coupling may occur. On the other hand, in the photoacoustic apparatus, since a pulse voltage is applied to the light source, the potential on the substrate fluctuates at high speed. In such a case, the energy leaks to the heat radiating mechanism side, which may cause a problem that a desired pulse waveform cannot be obtained.

  The present invention has been made in view of such a problem of the prior art, and an object thereof is to efficiently drive a semiconductor light emitting element.

The photoacoustic probe according to the present invention is:
A photoacoustic probe comprising: a light source substrate; and a probe that receives an acoustic wave generated from a subject by light emitted from the light source substrate and converts it into an electrical signal, wherein the light source substrate is connected in series. A light emitting element group including a plurality of semiconductor light emitting elements connected to the first surface is mounted on the first surface, and a return wiring connected to one end of the light emitting element group is opposite to the first surface Mounted on the second surface, the potential of the return wiring is constant regardless of the energization state of the semiconductor light emitting element.

The light source substrate according to the present invention is
A second light emitting element group composed of a plurality of semiconductor light emitting elements connected in series is mounted on the first surface, and a return wiring connected to one end of the light emitting element group is opposite to the first surface. A light source substrate mounted on a surface, wherein the potential of the return wiring is constant regardless of the energized state of the semiconductor light emitting element.

  According to the present invention, the semiconductor light emitting device can be driven efficiently.

The system block diagram of the photoacoustic apparatus which concerns on embodiment. The schematic diagram of the probe 180 which concerns on embodiment. The block diagram of the light source part and drive part in 1st embodiment. The wiring diagram of the light source part and drive part in 1st embodiment. FIG. 6 is a structural diagram of a contact portion of a connector. The figure explaining the modification of 1st embodiment. The block diagram of the light source part and drive part in 2nd embodiment. The wiring diagram of the light source part and drive part in 2nd embodiment. The block diagram of the light source part and drive part in 3rd embodiment. The wiring diagram of the light source part and drive part in 3rd embodiment. The block diagram of the light source part and drive part in the modification of 3rd embodiment. The wiring diagram of the light source part and drive part in the modification of 3rd embodiment. The block diagram of the light source part and drive part in 4th embodiment. The wiring diagram of the light source part and drive part in 4th embodiment.

  Embodiments of the present invention will be described below with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described below should be appropriately changed depending on the configuration of the apparatus to which the invention is applied and various conditions. Therefore, the scope of the present invention is not intended to be limited to the following description.

  The present invention relates to a technique for detecting acoustic waves propagating from a subject, generating characteristic information inside the subject, and acquiring the characteristic information. Therefore, the present invention can be understood as a photoacoustic apparatus (subject information acquisition apparatus), a control method thereof, or an object information acquisition method.

  The photoacoustic apparatus (subject information acquisition apparatus) according to the present invention receives acoustic waves generated in the subject by irradiating the subject with light (electromagnetic waves), and uses the characteristic information of the subject as image data. It is a device that uses the photoacoustic effect to be acquired. In this case, the characteristic information is characteristic value information corresponding to each of a plurality of positions in the subject, which is generated using a reception signal obtained by receiving a photoacoustic wave.

The characteristic information acquired by photoacoustic measurement is a value reflecting the absorption rate of light energy. For example, a generation source of an acoustic wave generated by light irradiation, an initial sound pressure in a subject, a light energy absorption density or absorption coefficient derived from the initial sound pressure, and a concentration of a substance constituting a tissue are included.
Further, based on photoacoustic waves generated by light having a plurality of different wavelengths, spectral information such as the concentration of a substance constituting the subject can be obtained. The spectroscopic information may be oxygen saturation, a value obtained by weighting the oxygen saturation with an intensity such as an absorption coefficient, a total hemoglobin concentration, an oxyhemoglobin concentration, or a deoxyhemoglobin concentration. Further, it may be glucose concentration, collagen concentration, melanin concentration, or volume fraction of fat or water.

  A two-dimensional or three-dimensional characteristic information distribution is obtained based on the characteristic information of each position in the subject. The distribution data can be generated as image data. The characteristic information may be obtained not as numerical data but as distribution information of each position in the subject. That is, distribution information such as initial sound pressure distribution, energy absorption density distribution, absorption coefficient distribution, and oxygen saturation distribution.

  The acoustic wave in this specification is typically an ultrasonic wave, and includes an elastic wave called a sound wave or a photoacoustic wave. An electric signal converted from an acoustic wave by a probe or the like is also called an acoustic signal. However, the description of ultrasonic waves or acoustic waves in this specification is not intended to limit the wavelength of those elastic waves. An acoustic wave generated by the photoacoustic effect is called a photoacoustic wave or an optical ultrasonic wave. An electrical signal derived from a photoacoustic wave is also called a photoacoustic signal. In this specification, the photoacoustic signal is a concept including both an analog signal and a digital signal. The distribution data is also called photoacoustic image data or reconstructed image data.

  The present invention relates to a method for mounting a light source unit of a photoacoustic apparatus that converts photoacoustic waves generated due to light emitted from a plurality of semiconductor light emitting elements into photoacoustic signals. In particular, the invention is based on a mounting form that makes it possible to reduce unnecessary radiation and realize a desired drive waveform while improving heat dissipation.

(First embodiment)
<System configuration>
The photoacoustic apparatus according to the first embodiment is an apparatus that generates a blood vessel image (structure image) in a subject by irradiating the subject with pulsed light and receiving a photoacoustic wave generated in the subject. is there.
Hereinafter, the configuration of the photoacoustic apparatus according to the first embodiment will be described with reference to FIG. The photoacoustic apparatus according to the first embodiment includes a probe 180, a signal collection unit 140, a computer 150, a display unit 160, and an input unit 170. The probe 180 includes a light source unit 200, a driving unit 300, and a receiving unit 120.

Here, an outline of photoacoustic measurement for the subject will be described.
First, the driving unit 300 controls the light source unit 200 on which a plurality of semiconductor light emitting elements are mounted to generate pulsed light and irradiate the subject. Thereby, an acoustic wave is periodically generated from the subject 100. In order to improve the S / N ratio of the signal, it is desirable to emit pulsed light a plurality of times and add the obtained signals.

  The receiving unit 120 receives a photoacoustic wave generated from the subject 100 and outputs an analog electric signal. Then, the signal collection unit 140 converts the analog signal output from the reception unit 120 into a digital signal and outputs the digital signal to the computer 150.

The computer 150 stores the digital signal output from the signal collection unit 140 in each light emission in a storage unit (not shown) as an electrical signal derived from the photoacoustic wave. In order to improve the S / N ratio, signals obtained by emitting a plurality of light pulses may be averaged.
In addition, the computer 150 generates photoacoustic image data by performing processing such as image reconstruction on the digital signal stored in the storage unit. The photoacoustic image data is displayed on the display unit 160.

  A user (physician, engineer, or the like) of the apparatus can make a diagnosis by checking the photoacoustic image displayed on the display unit 160. The display image may be stored in a memory in the computer 150 or a data management system connected to the photoacoustic apparatus via a network based on a storage instruction from the user or the computer 150. A user of the apparatus can input to the apparatus via the input unit 170.

Next, details of each component will be described.
<< Probe 180 >>
FIG. 2A is a schematic diagram of the probe 180 according to the present embodiment. Probe 180 is
A light source unit 200, a driving unit 300, a receiving unit 120, and a housing 181 are included.
The housing 181 is a housing that houses the light source unit 200, the driving unit 300, and the receiving unit 120. The user can use the probe 180 as a handheld probe by gripping the housing 181.
The housing 181 may also serve as a heat dissipation mechanism using a material having high thermal conductivity, as will be described later. The light source unit 200 is a light source that irradiates a subject with a light pulse. As described above, the light source unit 200 is driven by the driving unit 300 to emit light pulses. Note that the XYZ axes in the figure indicate coordinate axes when the probe is left stationary, and do not limit the orientation when the probe is used.
A probe 180 illustrated in FIG. 2A is connected to the signal collection unit 140 via a cable 182. The cable 182 includes a wiring for supplying power to the light source unit 200, a wiring for transmitting a light emission control signal, a wiring for outputting an analog signal output from the receiving unit 120 to the signal collecting unit 140 (all not shown). . Note that a connector may be provided on the cable 182 so that the probe 180 and the other components of the photoacoustic apparatus can be detached.

<< Light Source 200 >>
The light source unit 200 is a means for generating light that irradiates the subject 100.
FIG. 2B shows a YZ sectional view of the light source unit 200. In the light source unit 200, the semiconductor light emitting element groups 200A and 200B are mounted on one side of the printed circuit board 200-BD. Since the semiconductor light emitting elements 200A and 200B are mechanically weak and easily damaged, they are covered with a transparent protective cover 202. Moreover, the heat sink 203 is installed on the surface of the printed circuit board 200-BD on which the semiconductor light emitting elements 200A and 200B are not mounted via an insulator. The heat radiating plate 203 may be a heat radiating mechanism using the housing 181. Further, a mechanism for radiating heat using a heat pipe or the like may be used. The light source unit 200 may be electrically connected with a connector or the like so that it can be easily replaced in the event of a failure. Details of the light source unit will be described later.

In FIG. 2A, the light source unit 200 is installed only on one side of the receiving unit 120, but may be installed facing the receiving unit 120. With such a structure, it is possible to irradiate the subject with light pulses more uniformly.
In the present embodiment, an example in which 16 laser diodes are used will be described. However, the number of semiconductor light emitting elements may be increased or decreased depending on a necessary light amount. Further, the light source unit 200 may be mounted in any arrangement depending on conditions such as the shape of the probe as long as the subject can be irradiated with light pulses satisfactorily.
Also, the type of the semiconductor light emitting element is not limited to the laser diode (LD), but may be a light emitting diode (LED). The type and number of semiconductor light emitting elements are determined from the required light intensity.

  The pulse width of the light emitted from the light source unit 200 is, for example, not less than 10 nanoseconds and not more than 1 microsecond. The light wavelength of the light source unit 200 is preferably 400 nm or more and 1600 nm or less, but may be other wavelengths. The wavelength may be determined according to the light absorption characteristics of the light absorber to be imaged. For example, when imaging a blood vessel with high resolution, a wavelength (400 nm or more and 800 nm or less) at which absorption in the blood vessel is large may be used. In addition, when imaging a deep part of a living body, light having a wavelength (700 nm or more and 1100 nm or less) with less absorption in a background tissue (such as water or fat) of the living body may be used.

<< Driver 300 >>
The driving unit 300 is means for driving the semiconductor light emitting element groups 200A and 200B (that is, controlling the current to emit light) using a transistor such as a MOSFET as a switching element. As described above, the optical pulse width used in the photoacoustic apparatus is 10 nanoseconds or more and 1 microsecond or less, and it is necessary to flow a large current of about 10 A within this time. For this reason, if there is a small inductance component on the circuit, the drive waveform is distorted, and there is a possibility that the semiconductor light emitting elements 200A and 200B cannot be driven with a desired current value. That is, it is necessary to make the inductance component as small as possible. Details of the method for this and the drive unit 300 will be described later together with the embodiment of the light source unit 200.

<< Receiver 120 >>
The receiving unit 120 is a unit that includes a transducer (acoustic wave detection element) that receives a photoacoustic wave generated due to pulsed light and outputs an electrical signal, and a support that supports the transducer.
Examples of members constituting the transducer include a piezoelectric material, a capacitive transducer (CMUT), and a transducer using a Fabry-Perot interferometer. Examples of the piezoelectric material include a piezoelectric ceramic material such as PZT (lead zirconate titanate) and a polymer piezoelectric film material such as PVDF (polyvinylidene fluoride).
The electrical signal obtained by the transducer is a time-resolved signal. That is, the amplitude of the obtained electrical signal is a value based on the sound pressure received by the transducer at each time (for example, a value proportional to the sound pressure).

In addition, it is preferable to use what can detect the frequency component (typically 100 KHz to 10 MHz) which comprises a photoacoustic wave for a transducer. Alternatively, a plurality of transducers may be arranged side by side on the support to form a plane or curved surface called a 1D array, 1.5D array, 1.75D array, or 2D array.
The receiving unit 120 may include an amplifier that amplifies a time-series analog signal output from the transducer. The receiving unit 120 may include an A / D converter that converts a time-series analog signal output from the transducer into a time-series digital signal. That is, the receiving unit 120 may also serve as the signal collecting unit 140.

<< Signal collector 140 >>
The signal collection unit 140 includes an amplifier that amplifies an analog electrical signal output from the reception unit 120 for each light emission of the light source unit 200, and an A / D converter that converts the analog signal output from the amplifier into a digital signal. Including. The signal collection unit 140 may be configured by an FPGA (Field Programmable Gate Array) chip or the like.

  Analog signals output from a plurality of transducers arranged in an array in the receiving unit 120 are amplified by a plurality of amplifiers corresponding to each, and converted into digital signals by a plurality of A / D converters corresponding to each. The A / D conversion rate is preferably at least twice the bandwidth of the input signal. For example, when the frequency component constituting the photoacoustic wave is 100 KHz to 10 MHz, the A / D conversion rate is 20 MHz or more, preferably 40 MHz or more.

  The signal collection unit 140 may be disposed inside the housing 181. With such a configuration, information between the probe 180 and the computer 150 can be propagated as a digital signal, so that noise resistance is improved. In addition, the number of wires can be reduced compared to the case of transmitting an analog signal, and the operability of the probe 180 is improved.

<< Computer 150 >>
The computer 150 is calculation means (information processing means in the present invention) including a calculation unit, a storage unit, and a control unit (all not shown). The unit responsible for the calculation function as the calculation unit can be configured by a processor such as a CPU or a GPU (Graphics Processing Unit), or an arithmetic circuit such as an FPGA (Field Programmable Gate Array) chip. These units may be composed of a single processor or arithmetic circuit, or may be composed of a plurality of processors or arithmetic circuits.
For example, the computer 150 sets a pulse width and a pulse shape of light emitted from the light source unit 200 for the driving unit 300.

The computer 150 performs the following processing for each of the plurality of transducers.
First, the computer 150 adds and averages data at the same time based on the light emission time for a plurality of digital signals (photoacoustic signals) output from the signal collection unit 140 for each light emission of the pulsed light. The photoacoustic signal that has been averaged is stored in the storage unit as a combined photoacoustic signal.
Then, the calculation unit reconstructs an image based on the combined photoacoustic signal stored in the storage unit, and generates a photoacoustic image (structure image or functional image) and performs other calculation processing. . Note that the calculation unit may acquire various parameters such as the sound speed inside the subject and the configuration of the holding unit via the input unit 170.

  The reconstruction algorithm used when the arithmetic unit converts the photoacoustic signal into a photoacoustic image (for example, three-dimensional volume data) includes a back projection method in the time domain, a back projection method in the Fourier domain, and a model-based method (repetition Arbitrary methods such as an arithmetic method) can be adopted. Examples of back projection methods in the time domain include universal back projection (UBP), filtered back projection (FBP), and phasing addition (delay and sum).

The storage unit includes a volatile memory such as a RAM (Random Access Memory), a non-temporary storage medium such as a ROM (Read only memory), a magnetic disk, and a flash memory. Note that the storage medium storing the program is a non-temporary storage medium. The storage unit may be composed of a plurality of storage media.
The storage unit can store various types of data such as the photoacoustic signal that has been averaged, the photoacoustic image data generated by the arithmetic unit, and the reconstructed image data based on the photoacoustic image data.

A control part is a means to control operation | movement of each component of a photoacoustic apparatus, and is comprised by arithmetic elements, such as CPU. The control unit transmits an emission control signal of an optical pulse and an optical pulse waveform setting signal to the driving unit 300, whereby the semiconductor light emitting element emits light with the specified optical pulse waveform and irradiates the subject.
Further, the control unit reads the program code stored in the storage unit and controls the operation of each component of the photoacoustic apparatus.
In addition, the control unit adjusts an image output to the display unit 160. For example, image processing for display and processing for combining graphics for GUI may be performed on the obtained photoacoustic image data as necessary. Thereby, an oxygen saturation distribution image is sequentially displayed with the movement of the probe and the photoacoustic measurement.

  The computer 150 may be a workstation designed exclusively, or may operate a general-purpose PC or workstation according to a program stored in the storage unit. Each configuration of the computer 150 may be configured by different hardware. Further, at least a part of the configuration of the computer 150 may be configured by a single hardware.

<< Display unit 160 >>
The display unit 160 is a display such as a liquid crystal display or an organic EL, and is an apparatus that displays an image representing object information (for example, structural information or function information) obtained by the computer 150, a numerical value at a specific position, and the like. The display unit 160 is a GUI for operating images and devices.
May be displayed. Note that the image output to the display unit 160 may be processed (e.g., brightness value adjustment) by the computer 150 or the display unit 160.

<< Input unit 170 >>
The input unit 170 is a means for acquiring input such as instructions and numerical values from the user. The input unit 170 may be, for example, an operation console including a mouse and a keyboard that can be operated by the user. When a touch panel is used as the display unit 160, the display unit 160 may also serve as the input unit 170. The user can use the input unit 170 to perform operations such as measurement start / end and image save instruction. Further, the input unit 170 may acquire various parameter inputs related to the sound speed inside the subject, the configuration of the holding unit, and the like, and the computer 150 may perform processing using the information.

  The constituent elements of the photoacoustic apparatus described above may be configured as separate apparatuses, or may be configured as a whole. Further, at least a part of the configuration of the photoacoustic apparatus may be integrated, and the rest may be configured by another apparatus.

<< Subject 100 >>
The subject 100 does not constitute the photoacoustic apparatus according to the present invention, but will be described below. The photoacoustic apparatus according to the present embodiment can be used for the purpose of diagnosing malignant tumors, vascular diseases, etc. of humans and animals, and monitoring the progress of chemical treatment. Therefore, the subject 100 is assumed to be a living body, specifically, a target region for diagnosis such as breasts of human bodies or animals, each organ, blood vessel network, head, neck, abdomen, extremities including fingers and toes. The For example, if the human body is a measurement target, oxyhemoglobin or deoxyhemoglobin, a blood vessel containing many of them, or a new blood vessel formed in the vicinity of a tumor may be used as a light absorber. Further, a plaque of the carotid artery wall or the like may be a target of the light absorber. In addition, a dye such as methylene blue (MB) or indocyanine green (ICG), gold fine particles, or a substance introduced from the outside, which is accumulated or chemically modified, may be used as the light absorber. Moreover, it is good also considering the light absorber attached | subjected to the puncture needle and the puncture needle as an observation object. The subject may be an inanimate object such as a phantom or a test object.

<Details of the light source>
Next, the configuration of the light source unit 200 and the drive unit 300 in the first embodiment will be described with reference to FIG. As shown in FIG. 1, the light source unit 200 includes two sets of semiconductor light emitting element groups (200A, 200B) connected in series. The semiconductor light emitting element group 200A includes eight laser diodes (200a to 200h), and the semiconductor light emitting element group 200B includes eight laser diodes (200i to 200p). These semiconductor light emitting element groups 200A and 200B are mounted on one side (A side, the first side in the present invention) of the printed circuit board 200-BD. A wiring (return wiring) 200-BP that supplies a pulse voltage to the anodes of the semiconductor light emitting element groups 200A and 200B is patterned on the opposite surface (B surface, the second surface in the present invention) of the printed circuit board 200-BD. Implemented. The wirings on the A and B sides are connected by through holes 200-TH1 and 200-TH2. That is, one end of the semiconductor light emitting element group is connected to the return wiring through the through hole.

  In this specification, the wiring connecting the wirings on the A and B sides is described as a through-hole, but it may be formed by a method using a through via or may be realized by fitting. Moreover, the form which solders a copper wire, a copper plate, etc. outside a printed circuit board, and connects the wiring of A surface and B surface may be sufficient. In this specification, these mounting forms are collectively referred to as a through hole.

In addition, the return wiring 200-BP is a single planar wiring having a large area, but it is sufficient that there is a pattern at least in a place facing the semiconductor light emitting element groups 200A and 200B. The drive current of the high frequency component that flows through the semiconductor light emitting element groups 200A and 200B flows through a portion with a small inductance. That is, the current concentrates on the return wiring 200-BP disposed on the back surfaces of the semiconductor light emitting element groups 200A and 200B. Therefore, the effect of reducing the inductance can be realized by making the return wiring 200-BP one planar wiring having a large area. Further, the return wiring may be divided for each of the semiconductor light emitting element groups 200A and 200B.

  FIG. 1B is an α-β cross section of the light source substrate shown in FIG. As can be seen from FIG. 1B, the opening of the current flowing through the semiconductor light emitting element groups 200A and 200B is proportional to the thickness and length of the printed circuit board 200-BD. Since the length cannot be shortened due to the area to be illuminated, it is effective to reduce the thickness of the printed board in order to reduce the opening. Further, since the heat dissipation mechanism is provided on the B surface as described above, for example, it is effective to reduce the thickness of the printed circuit board in order to reduce the thermal resistance from the semiconductor light emitting element groups 200A and 200B to the heat dissipation mechanism. is there. For example, a glass epoxy board is suitable for the printed board from the viewpoint of strength when it is thinned. From the viewpoint of heat dissipation, a flexible substrate that can be made thin, an alumina substrate having a low thermal resistance, a metal core substrate, and the like are effective.

FIG. 4 is a wiring diagram of the light source substrate. The circles indicated by reference numerals 200-K1, 200-K2, 200-A1, 200-A2 correspond to the contact portions of the connector of the printed circuit board 200-BD. In addition, the code | symbol of the contact part of the connector connected to printed circuit board 200-BD is abbreviate | omitted. Moreover, the square shown with a dotted line shows the range mounted in printed circuit board 200-BD. Reference numerals 300a and 300b are transistors such as Nch MOSFETs, which control currents flowing through the semiconductor light emitting elements 200A and 200B of the light source unit 200, respectively. Reference numeral 300 c denotes a power source that supplies power to the semiconductor light emitting element of the light source unit 200. When the probe is a handheld type, the power supply 300c may be mounted on the photoacoustic apparatus main body outside the probe and supply power. In this case, in order to lower the impedance (inductance component) of the power supply, a bypass capacitor (not shown) may be mounted in the probe.
By controlling the gate voltages of the transistors 300a and 300b, the current flowing through the semiconductor light emitting element groups 200A and 200B of the light source unit 200 can be controlled. These waveforms may be the same waveform or different waveforms. By realizing such a drive unit 300, the semiconductor light emitting element groups 200A and 200B can emit light with a desired optical pulse waveform.

The structure of the contact portion of the connector is shown in FIG. In the present embodiment, since the electrodes are arranged facing the front and back at the end portion of the substrate, a plurality of terminals can be connected by one connector. Such an arrangement is particularly advantageous because the inductance component is reduced.
FIG. 5A shows the best connector structure. This structure is a structure in which an unnecessary wiring length does not occur between the connector contacts 201c and 201d and the connector terminal portions 201a and 201b when they are fitted to the contact portions arranged on the A and B surfaces of the printed circuit board. It is. That is, the inductance component can be reduced.
On the other hand, the structure shown in FIG. 5B is a structure in which an extra wiring length is generated between the connector contacts 201c and 201d and the connector terminal portions 201a and 201b at the time of fitting. In this case, the inductance component is slightly increased. When the rise and fall times of the drive current waveforms of the semiconductor light emitting element groups 200A and 200B are short, the structure is somewhat disadvantageous.

As described above, when a heat dissipation mechanism is provided on the B surface, capacitive coupling occurs between the return wiring 200-BP and the heat dissipation mechanism. When the voltage of the return wiring 200-BP varies, a current flows between the return wiring 200-BP and the heat dissipation mechanism. In addition, this current causes unnecessary radiation to the outside, and the drive waveform changes.
Therefore, in the light source substrate according to the first embodiment of the present invention, the voltage of the power source 300c is directly applied to the return wiring 200-BP. That is, the potential of the return wiring 200-BP does not change regardless of the energized state. As a result, unnecessary radiation to the outside can be prevented, and changes in the drive waveform can be prevented.

Another form of the first embodiment is shown in FIG.
FIG. 6A shows a form in which the connector portion of the printed circuit board 200-BD is taken out from the longitudinal surface. In this way, since it is not necessary to connect a connector in the longitudinal direction, the length in the longitudinal direction can be shortened. This is particularly effective when the length of the probe 180 in the X direction is limited. Such a shape of the printed circuit board is effective when a flexible substrate cannot be used.

FIG. 6B shows a form in which the directions of the semiconductor light emitting element group 200A and the semiconductor light emitting element group 200B are reversed. In such a configuration, the directions of the currents flowing through the semiconductor light emitting element group 200A and the semiconductor light emitting element group 200B are reversed, so that the generated magnetic field is canceled out, and unnecessary radiation can be reduced more satisfactorily.
FIG. 6C shows a form in which the semiconductor light emitting element group 200A and the semiconductor light emitting element group 200B are reversed in direction and the connector portion of the printed circuit board 200-BD is taken out of the longitudinal surface. It has both features mentioned above.

  As described above, according to the first embodiment, it is possible to drive the semiconductor light emitting element group while keeping the potential of the return wiring constant. That is, since capacitive coupling does not occur between the return wiring and the heat dissipation mechanism, unnecessary radiation can be reduced, and the semiconductor light emitting element can be driven with a desired driving waveform.

(Second embodiment)
Next, a second embodiment of the present invention will be described. The configuration of the photoacoustic apparatus of the second embodiment is the same as that of the first embodiment, and only the configuration of the light source substrate is different. A mounting form of the light source unit 200 of the second embodiment is shown in FIG. 7, and circuits of the light source unit 200 and the driving unit 300 are shown in FIG.

The light source substrate according to the second embodiment is different from the first embodiment in that the PchMOSFET is used instead of the NchMOSFET and the anode and cathode directions of the semiconductor light emitting element groups 200A and 200B are mounted in reverse. Is different.
In FIG. 8, the circles indicated by reference numerals 200-K1, 200-K2, 200-A1, 200-A2 correspond to the contact portions of the connector of the printed circuit board 200-BD.
Reference numerals 300d and 300e are transistors such as PchMOSFETs, which control currents flowing through the semiconductor light emitting elements 200A and 200B of the light source unit 200, respectively.
Also in the second embodiment, as in the first embodiment, by controlling the gate voltages of the transistors 300d and 300e, the current flowing through the semiconductor light emitting element groups 200A and 200B of the light source unit 200 can be controlled. .

As can be seen from FIGS. 7 and 8, in the second embodiment, the return wiring 200-BP becomes the ground voltage. That is, there is no change in voltage regardless of the current flowing through the semiconductor light emitting element groups 200A and 200B. Therefore, as in the first embodiment, the potential of the return wiring 200-BP does not change at a high frequency. Therefore, as in the first embodiment, unnecessary radiation can be reduced, and the semiconductor light emitting element can be driven with a desired driving waveform.
Note that the arrangement of the connector portions described in the first embodiment can also be applied to the second embodiment.

(Third embodiment)
Next, a third embodiment of the present invention will be described. The configuration of the photoacoustic apparatus according to the third embodiment is the same as that of the first embodiment, and only the configuration of the light source substrate is different. A mounting form of the light source unit 200 of the third embodiment is shown in FIG. 9, and circuits of the light source unit 200 and the driving unit 300 are shown in FIG.
A part in a square indicated by a dotted line represents a part mounted on the printed circuit board 200-BD. That is, the third embodiment is an embodiment in which a part of the circuit of the driving unit 300 is mounted on the printed board 200-BD.

As shown in FIG. 9, the light source unit 200 in the third embodiment is composed of two sets of semiconductor light emitting element groups 200A and 200B, as in the first embodiment. These semiconductor light emitting element groups 200A and 200B are mounted on one surface (A surface) of the printed circuit board 200-BD.
Further, Nch MOSFETs (300a, 300b) for supplying a voltage to the cathodes of the semiconductor light emitting element groups 200A, 200B are inserted on the B surface. The wirings on the A and B sides are connected by through holes 200-TH1 and 200-TH2.

  The source electrodes of the Nch MOSFETs (300a, 300b) are connected to the GND wiring 200-GP mounted on the B surface of the printed board 200-BD. The GND wiring 200-GP is also a wiring for returning a current flowing through the semiconductor light emitting element groups 200A and 200B, that is, a return wiring. In the figure, the GND wiring 200-GP is a single planar wiring having a large area. However, it is sufficient that there is a pattern at least in a place where the semiconductor light emitting element groups 200A and 200B are opposed to each other. The GND wiring 200-GP may be provided separately for each semiconductor light emitting element group.

In the third embodiment, the bypass capacitor 200-C is mounted in order to reduce the area of the opening. The capacity of the bypass capacitor 200-C is preferably set to be equal to or larger than the capacity capable of storing the charge required for the light source unit to emit light once. Note that a bypass capacitor 200-C having a larger capacity may be provided outside the printed circuit board 200-BD.
By mounting the bypass capacitor 200-C, the current of high frequency components is reduced. Therefore, it is not always necessary to use the card edge connector as described above as a connector for supplying power to the light source unit 200.

  In the third embodiment, the GND wiring 200-GP, which is the return wiring arranged on the B surface, becomes the ground voltage. Therefore, as in the first and second embodiments, no alternating current flows between the return wiring and the heat dissipation mechanism.

(Modification of the third embodiment)
Although the Nch MOSFET is used in the third embodiment, a Pch MOSFET can also be adopted. FIG. 11 is a diagram illustrating a mounting form of the light source unit 200 in the present modification, and FIG. 12 is a diagram illustrating a circuit of the light source unit 200 and the driving unit 300. In this modification, the return wiring on the B surface is the power supply wiring 200-PP, and the power supply voltage is applied.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described. The configuration of the photoacoustic apparatus of the fourth embodiment is the same as that of the first embodiment, and only the configuration of the light source substrate is different. FIG. 13 shows a mounting form of the light source unit 200 according to the fourth embodiment, and FIG. 14 shows circuits of the light source unit 200 and the driving unit 300.

  In the fourth embodiment, inductors 300f and 300g for supplying a voltage to the anodes of the semiconductor light emitting element groups 200A and 200B are mounted on the other surface (B surface) of the printed circuit board 200-BD. The wirings on the A and B sides are connected by through holes 200-TH1 and 200-TH2.

The other electrodes of the inductors 300f and 300g are connected to the return wiring 200-BP mounted on the B surface of the printed board 200-BD. Furthermore, the diodes 300h and 300i are mounted on the B surface and connected between the return wiring 200-BP and the cathodes of the semiconductor light emitting element groups 200A and 200B.

Reference numerals 300a and 300b are transistors such as Nch MOSFETs, for example, which perform ON / OFF control of currents flowing through the semiconductor light emitting element groups 200A and 200B of the light source unit 200, respectively.
Reference numerals 300f and 300g denote inductors, which are realized by, for example, coils or wiring of a printed board. When controlling the semiconductor light emitting element groups 200A and 200B with different pulse widths, the inductors 300f and 300g are designed to have different inductances. Specifically, the inductance may be reduced as the pulse width becomes shorter.
Reference numerals 300h and 300i denote diodes that play a role of returning the current flowing from the inductors 300f and 300g to the semiconductor light emitting element groups 200A and 200B to the inductors 300f and 300g when the transistors 300a and 300b are turned off.

  Reference numeral 300j denotes a variable voltage power source. Here, when each pulse width can be set, the variable voltage power supply 300j may have two systems, and the voltage may be set independently. When a handheld probe is employed, the variable voltage power supply 300j may be mounted on the photoacoustic apparatus main body outside the probe. In this case, in order to reduce the impedance (inductance component) of the power source, a bypass capacitor (not shown) or the like may be mounted in the probe.

  When the transistor 300a is turned on, the difference voltage between the sum of the forward voltages of the semiconductor light emitting element group 200A and the drain-source voltage of the transistor 300a and the output voltage of the variable voltage power supply 300j is the inductor 300f. To be applied. The slope of the current flowing through the inductor 300f is determined by the voltage applied to the inductor 300f and the inductance of the inductor 300f. That is, when the inductance is fixed, the slope of the current flowing through the inductor 300f can be increased by increasing the voltage of the variable voltage power supply 300j. That is, the slope of the current flowing through the semiconductor light emitting element group 200A can be controlled. In other words, the rising waveform of the optical pulse can be determined.

When the transistor 300a is turned off, the voltage applied to the inductor 300f is the sum of the forward voltage of the semiconductor light emitting element group 200A and the forward voltage of the diode 300h. The slope of the current flowing through the inductor 300f is determined by this voltage and the inductance of the inductor 300f. That is, the falling waveform of the optical pulse is determined.
For example, consider a case where the drain-source voltage when the transistor 300a is ON and the forward voltage of the diode 300h are sufficiently smaller than the sum of the forward voltages of the semiconductor light emitting element group 200A. In this case, if the output voltage of the variable voltage power supply 300j is set to twice the sum of the forward voltages of the semiconductor light emitting element group 200A, the slopes of the rising and falling waveforms of the current flowing through the semiconductor light emitting element group 200A Can be the same. That is, the slope of the rising waveform and the falling waveform of the optical pulse waveform can be made substantially the same.
Further, by connecting the anode of the diode 300h to the other electrode of the inductor 300f, the fall time of the current flowing through the semiconductor light emitting element group 200A when the transistor 300a is turned off can be shortened. In this manner, a desired optical pulse waveform can be obtained using the inductor 300f and the variable voltage power supply 300j.

  Similarly, the slope of the rising waveform and falling waveform of the current flowing through the semiconductor light emitting element group 200B, that is, the optical pulse waveform can be controlled to a desired waveform using the inductor 300g and the variable voltage power supply 300j.

In the fourth embodiment, the return wiring 200-BP arranged on the B surface becomes the power supply voltage.
Therefore, as in the other embodiments, no alternating current flows between the return wiring and the heat dissipation mechanism.
In the fourth embodiment, an Nch MOSFET can be used as the switching transistor. In this case, the return wiring becomes the ground voltage.

(Other embodiments)
The description of each embodiment is an exemplification for explaining the present invention, and the present invention can be implemented with appropriate modifications or combinations without departing from the spirit of the invention.
For example, the present invention can be implemented as a photoacoustic probe, a light source substrate, and a photoacoustic apparatus that include at least a part of the above features. The above processes and means can be freely combined and implemented as long as no technical contradiction occurs.

  For example, in the description of the embodiment, each of the semiconductor light emitting element groups 200A and 200B has a light source formed by connecting eight laser diodes in series, but the number of laser diodes to be connected is not limited thereto. Further, the number of semiconductor light emitting element groups is not limited to two. For example, more configurations may be used. The number of semiconductor light emitting elements and the number of semiconductor light emitting element groups can be determined based on the required light quantity, the type of current waveform that drives the laser diode, the rating of the transistor, and the like.

  Further, the light emitted from the light source 200 may have a plurality of wavelengths. When a plurality of wavelengths are used, oxygen saturation as functional information can be calculated. For example, it is possible to obtain oxygen saturation after obtaining photoacoustic signals by alternately switching two wavelengths for each imaging frame rate and calculating reconstructed image data. Further, the photoacoustic apparatus according to the present invention may be additionally provided with a function of transmitting ultrasonic waves from a transducer and performing measurement using reflected waves. In this case, of course, the light source unit 200 does not emit light.

  In the description of the embodiment, the device in which the handheld probe and the photoacoustic apparatus main body are connected by wiring is exemplified. Also good. Thus, the present invention may be implemented as a hand-held probe alone or a light source substrate alone.

  120: reception unit, 140: signal collection unit, 151: calculation unit, 200: light source unit, 210: driver unit

Claims (9)

A photoacoustic probe comprising: a light source substrate; and a probe that receives an acoustic wave generated from a subject by light emitted from the light source substrate and converts the acoustic wave into an electrical signal,
The light source substrate is
A light emitting element group configured to include a plurality of semiconductor light emitting elements connected in series is mounted on the first surface,
A return wiring connected to one end of the light emitting element group is mounted on a second surface opposite to the first surface,
The photoacoustic probe, wherein the potential of the return wiring is constant regardless of the energized state of the semiconductor light emitting element. In the light source substrate,
An end portion of the light emitting element group to which the return wiring is not connected and an end portion of the return wiring to which the light emitting element group is not connected are arranged opposite to the front and back at one end of the light source substrate. The photoacoustic probe according to claim 1, wherein: In the light source substrate,
A switching element for applying a pulse voltage to the semiconductor light emitting element is connected to an end of the light emitting element group to which the return wiring is not connected,
The photoacoustic probe according to claim 1, wherein a power supply voltage or a ground voltage is applied to an end portion of the return wiring to which the light emitting element group is not connected. The photoacoustic probe according to any one of claims 1 to 3, wherein a heat dissipation mechanism is in contact with the second surface of the light source substrate via an insulator. In the light source substrate,
The element for driving the semiconductor light emitting element is provided at an end of the return wiring arranged on the second surface, which is connected to the light emitting element group. 5. The photoacoustic probe according to any one of items 1 to 4. In the light source substrate,
The photoacoustic probe according to claim 5, further comprising a capacitor capable of storing a charge necessary for causing the semiconductor light emitting element to emit light at least once. In the light source substrate,
The inductor is provided in the edge part connected to the said light emitting element group of the said return wiring arrange | positioned on said 2nd surface, The any one of Claim 1 to 4 characterized by the above-mentioned. Photoacoustic probe. A light emitting element group consisting of a plurality of semiconductor light emitting elements connected in series is mounted on the first surface,
A return wiring connected to one end of the light emitting element group is a light source substrate mounted on a second surface opposite to the first surface,
The light source substrate, wherein the potential of the return wiring is constant regardless of the energized state of the semiconductor light emitting element. The photoacoustic probe according to any one of claims 1 to 7,
Information processing means for acquiring characteristic information in the subject based on the electrical signal;
A photoacoustic apparatus comprising:

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