JP2016047114A - Photoacoustic imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoacoustic imaging apparatus capable of acquiring a clear acoustic image by causing a detection part to efficiently detect acoustic waves.SOLUTION: A photoacoustic imaging apparatus 100 comprises: light source parts 1a and 1b including three light-emitting parts 10a-10c performing pulse emission; a detection part 2 for detecting acoustic waves generated from a detection object in an analyte that absorbs light applied from the light-emitting parts 10a-10c; and a control part 30 that deviates pulse emission timing of the light-emitting parts 10a-10c, causes the light-emitting parts 10a-10c to sequentially emit light so as to overlap respective light pulses of the light-emitting parts 10a-10c with each other, generates composite waveforms of a plurality of light pulses of the light-emitting parts 10a-10c, and controls an amount of timing deviations of the pulse emissions to approximate a frequency of the composite waveforms to a frequency in which receiving sensitivity of the detection part 2 is maximized.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a photoacoustic imaging apparatus, and more particularly, to a photoacoustic imaging apparatus including a light source unit.

  Conventionally, a photoacoustic imaging apparatus including a light source unit is known (see, for example, Patent Document 1).

  Patent Document 1 discloses a photoacoustic imaging apparatus including a laser light source unit that emits pulsed light and a detection unit that detects an acoustic wave generated from a detection target in a subject that has absorbed the pulsed laser light. Is disclosed. The detection unit has sensitivity in a predetermined frequency band with respect to the acoustic wave to be detected. Note that the acoustic wave is generated from the subject when the intensity of the laser light is changed. Further, since the acoustic wave is generated as an ultrasonic wave having a pulse width similar to the optical pulse width of the laser light, the frequency corresponds to the optical pulse width.

  In the photoacoustic image generating apparatus of Patent Document 1, it is considered that the laser light source unit uses a solid-state laser.

JP2013-075000A

  However, in the photoacoustic image generation device described in Patent Document 1, the detection is performed when the frequency of the acoustic wave generated by the laser light from the solid-state laser does not match a predetermined frequency band that is highly sensitive in the detection unit. There is a problem that the detection efficiency of the acoustic wave in the part is deteriorated, and the image obtained based on the acoustic wave tends to be unclear.

  The present invention has been made to solve the above-described problems, and one object of the present invention is to obtain a clear acoustic image by efficiently detecting an acoustic wave in a detection unit. Is to provide a simple photoacoustic imaging apparatus.

  A photoacoustic imaging apparatus according to an aspect of the present invention includes an acoustic wave generated from a light source unit including a plurality of light emitting units that emit pulses and a detection target in a subject that has absorbed light emitted from the light emitting unit. The plurality of light emitting units are caused to emit light in order so that the light emission timings of the plurality of light emitting units overlap each other by shifting the pulse light emission timings of the detection unit and the plurality of light emitting units with respect to each other. And a control unit that controls the amount of deviation of the pulse emission timing so that the frequency of the combined waveform approaches the frequency at which the reception sensitivity of the detection unit is maximized.

  In the photoacoustic imaging apparatus according to one aspect of the present invention, as described above, the control unit generates a composite waveform of a plurality of optical pulses, and the frequency of the composite waveform is the frequency at which the reception sensitivity of the detection unit is maximized. By controlling the amount of deviation of the pulse emission timing so as to approach the frequency, the frequency of the combined waveform can be brought close to the frequency at which the detection sensitivity of the detection unit is maximized, so that it is not detected by the detection unit (converted to heat) ) Laser light that becomes an acoustic wave can be prevented from being emitted from the light source unit. Therefore, an acoustic wave can be detected efficiently in the detection unit. As a result, a clear acoustic image can be obtained.

  In the photoacoustic imaging apparatus according to the above aspect, the control unit is preferably configured to perform control so that a plurality of light emitting units emit light in order such that three or more light pulses overlap each other. With this configuration, when three or more optical pulses overlap each other, the optical pulses are superimposed on each other near the center of the composite waveform by appropriately adjusting the shift amount. A waveform having a peak can be obtained. That is, since the synthesized waveform can be approximated to a triangular wave or a sine wave that easily generates an acoustic wave, the acoustic wave can be detected more efficiently in the detection unit. As a result, a clearer acoustic image can be obtained.

  In this case, the control unit is preferably configured to perform control so that the plurality of light-emitting units emit light in order so that odd and three or more light pulses overlap each other. With this configuration, when an odd number of three or more optical pulses overlap each other, the optical pulses are superimposed on each other near the center of the composite waveform by appropriately adjusting the shift amount. The waveform can have a peak at the center.

  In the photoacoustic imaging apparatus according to the above aspect, preferably further includes a switch for turning on and off the plurality of light emitting units, and the control unit turns on the switch so as to issue the plurality of light emitting units in order, The plurality of light emitting units are configured to shift the timing of pulse light emission from each other. With this configuration, noise (electromagnetic waves) that causes image disturbance that occurs during switching of each light emitting unit can be dispersed, so that the noise level can be reduced. As a result, a clearer acoustic image can be obtained.

  In the photoacoustic imaging apparatus according to the above aspect, preferably, four or more light pulses of the light emitting unit are provided, and the control unit is an optical pulse train formed by overlapping the light pulses of the four or more light emitting units. The first and last light pulses emitted at both ends and the light pulses adjacent to the light pulses at both ends are shifted by a first shift amount and between a plurality of light pulses sandwiched between the light pulses at both ends. Is controlled so as to shift the second shift amount smaller than the first shift amount. With this configuration, the plurality of optical pulses sandwiched between the optical pulses at both ends are denser than the optical pulses at both ends and the optical pulses adjacent to the optical pulses at both ends, so that the peak of the combined waveform is further increased. be able to. Therefore, a larger acoustic wave can be detected by the detection unit. As a result, a clearer acoustic image can be obtained.

  In the photoacoustic imaging apparatus according to the above aspect, the control unit is preferably configured to perform control so that the plurality of light emitting units emit light in order so that the combined waveform approximates a sine wave shape. With this configuration, since the synthesized waveform of the acoustic wave approaches a sine wave shape, the sound that becomes a harmonic component (for example, a frequency that is three times the fundamental frequency or a frequency that is five times the fundamental frequency) by frequency analysis. Appearance of waves is suppressed, and acoustic waves can be generated close to a single frequency (fundamental frequency). Therefore, it is possible to suppress the emission of laser light from the light source unit, which is an acoustic wave as a harmonic component that is not detected by the detection unit (converted into heat). As a result, an acoustic wave can be detected more efficiently in the detection unit, and a clearer acoustic image can be obtained.

  In this case, it is preferable that the deviation amount of the pulse light emission timings of the plurality of light emitting units is not more than half of the pulse width of the light pulse of the light emitting unit. With this configuration, the overlapping portion (time) of a plurality of light pulses becomes large, so that the synthesized waveform can be made closer to a sine wave shape.

  In the photoacoustic imaging apparatus according to the above aspect, the light emitting unit of the light source unit preferably includes a light emitting diode element. If comprised in this way, power consumption can be reduced by using a light emitting diode element with comparatively small power consumption.

  In the photoacoustic imaging apparatus according to the above aspect, the light emitting unit of the light source unit preferably includes an organic light emitting diode element. If comprised in this way, a photoacoustic imaging device can be reduced in size easily by using the organic light emitting diode element which is easy to make thin.

  In the photoacoustic imaging apparatus according to the above aspect, the light emitting unit of the light source unit preferably includes a solid-state laser. If comprised in this way, a clearer acoustic image can be acquired by using the solid-state laser which radiate | emits a laser beam with high output.

  According to the present invention, as described above, a clear acoustic image can be obtained by efficiently detecting an acoustic wave in the detection unit.

It is the perspective view which showed the whole structure of the photoacoustic imaging device by 1st Embodiment of this invention. 1 is a block diagram illustrating an overall configuration of a photoacoustic imaging apparatus according to a first embodiment of the present invention. It is the figure which showed the spectrum characteristic of the detection part of the photoacoustic imaging device by 1st Embodiment of this invention. It is the figure which looked at the detection part and light source part of the photoacoustic imaging device by 1st Embodiment of this invention from the subject side. It is the figure which showed the light emission timing of each light emission part of the photoacoustic imaging device by 1st Embodiment of this invention. It is the figure which showed three rectangular waves and its synthetic waveform by 1st Embodiment of this invention. It is the figure which showed three triangular waves and its synthetic waveform by 1st Embodiment of this invention. It is the perspective view which showed the whole structure of the photoacoustic imaging device by 2nd Embodiment of this invention. It is the figure which showed five rectangular waves and its synthetic waveform by 2nd Embodiment of this invention. It is the figure which showed five triangular waves which shifted predetermined | prescribed deviation | shift amount mutually from 2nd Embodiment of this invention, and its synthetic waveform. It is the figure which showed five triangular waves which shifted the 1st deviation | shift amount or the 2nd deviation | shift amount mutually with respect to 2nd Embodiment of this invention, and its synthetic waveform. It is the block diagram which showed the whole structure of the photoacoustic imaging device by the modification of this invention. It is the figure which showed the light pulse and synthetic | combination waveform of the solid-state laser of the photoacoustic imaging device by the modification of this invention.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below with reference to the drawings.

  First, the configuration of the photoacoustic imaging apparatus 100 according to the first embodiment of the present invention will be described with reference to FIGS.

(First embodiment)
As shown in FIGS. 1 and 2, the photoacoustic imaging apparatus 100 according to the first embodiment of the present invention includes light source units 1 a and 1 b, a detection unit 2, and a signal processing unit 3.

  Each of the light source units 1a and 1b includes a plurality of LED (light emitting diode) elements 11 and includes three light emitting units 10a to 10c (see FIGS. 2 and 4) that emit pulses. The detection unit 2 includes an ultrasonic vibration element 20. The detection unit 2 (ultrasonic vibration element 20) has sensitivity in a predetermined frequency band with respect to the acoustic wave AW to be detected. That is, the detection unit 2 has a predetermined frequency band in which the detected acoustic wave AW can be efficiently voltage-converted. Details will be described later. The signal processing unit 3 includes a control unit 30 and a display unit 31. The signal processing unit 3 is connected to the light source units 1a and 1b by a signal line 30a for transmitting power and signals. The signal processing unit 3 is connected to the detection unit 2 through a signal line 30b that transmits power and signals.

  The photoacoustic imaging apparatus 100 emits light to the subject P such as a human body from the light sources 1a and 1b, and generates an acoustic wave AW generated from the detection target Q in the subject P that has absorbed the irradiated light. The detection unit 2 is configured to detect. In addition, the photoacoustic imaging apparatus 100 is configured to image the detection target Q based on the acoustic wave AW detected by the detection unit 2. Further, the photoacoustic imaging apparatus 100 emits ultrasonic waves from the ultrasonic vibration element 20 to the subject P, and detects the ultrasonic waves reflected by the detection target Q in the subject P by the detection unit 2 (ultrasonic vibration). It is configured to be detected by element 20). Further, the photoacoustic imaging apparatus 100 is configured to be able to image the detection target Q based on the reflected ultrasonic waves detected by the detection unit 2. In addition, the frequency of the light irradiated to the detection target Q from the light sources 1a and 1b and the frequency of the acoustic wave AW generated from the detection target Q are substantially the same.

  In this specification, an ultrasonic wave is a sound wave (elastic wave) having a frequency that is high enough not to cause an auditory sensation in a person with normal hearing ability, and a sound wave (elastic wave) of about 16000 Hz or higher. To do. Further, in this specification, an ultrasonic wave generated when the detection target Q in the subject P absorbs light is referred to as an “acoustic wave” and is generated by the detection unit 2 (the ultrasonic vibration element 20). For convenience of explanation, the ultrasonic waves reflected on the detection object Q in the subject P are distinguished and described as “ultrasonic waves”.

  Here, in the first embodiment, the photoacoustic imaging apparatus 100 emits light so that a plurality of light pulses overlap each other by shifting the pulse emission timings of the light emitting units 10a to 10c with each other under the control of the control unit 30. The parts 10a to 10c are configured to emit light in order. Further, the photoacoustic imaging apparatus 100 is configured to generate a combined waveform of light pulses emitted in order from the light emitting units 10 a to 10 c under the control of the control unit 30. Further, in the photoacoustic imaging apparatus 100, the frequency of the combined waveform approaches the frequency Fmax (hereinafter referred to as the center frequency) (see FIG. 3) at which the reception sensitivity of the detection unit 2 is maximized under the control of the control unit 30. In this way, the amount of deviation of the pulse emission timing is controlled. That is, the photoacoustic imaging apparatus 100 is configured to generate an acoustic wave that can be efficiently voltage-converted in the detection unit 2 by synthesizing sequentially emitted light pulses under the control of the control unit 30. Has been. Details will be described later.

  Next, a detailed configuration of each part of the photoacoustic imaging apparatus 100 will be described.

  As shown in FIG. 4, the light source units 1 a and 1 b are arranged close to the detection unit 2. A pair of light source units 1 a and 1 b is provided on both sides of the detection unit 2 in the Y direction. In addition, since the light source parts 1a and 1b are comprised substantially symmetrically on both sides of the detection part 2, below, only the light source part 1a of the Y2 direction side is demonstrated.

  As shown in FIG. 1, the light source unit 1 a is configured to irradiate light toward the subject P. As a result, the light source unit 1a is configured to generate an acoustic wave AW from the detection target Q by causing the detection target Q in the subject P to absorb light. The light source unit 1a (LED element 11) is configured to generate light having substantially the same wavelength (for example, light having a wavelength of about 700 nm to 1000 nm).

  Moreover, as shown in FIG. 4, the light source part 1a is provided with three light emission parts 10a-10c. Each of the light emitting units 10a to 10c is composed of an LED element array having a plurality (21 pieces) of LED elements 11 arranged linearly in the X direction. The light emitting units 10a to 10c are arranged so that the light emitting unit 10a, the light emitting unit 10b, and the light emitting unit 10c are arranged in parallel from the detection unit 2 side (from the Y1 direction side). The light emitting units 10a to 10c are configured to generate optical pulses having the same waveform. Each of the light emitting units 10a to 10c emits a pulsed light to generate a rectangular light pulse (hereinafter referred to as a rectangular wave) (see FIG. 6) or a triangular light pulse (hereinafter referred to as a triangular wave) (see FIG. 6). 7). In the actual pulse waveform, since there is a limit to the rising and falling slopes, the rectangular wave becomes a trapezoidal waveform as shown in FIG.

  As shown in FIG. 2, the light emitting units 10a to 10c are provided with a light source driving circuit 12 and a switch 13, respectively.

  Each light source drive circuit 12 is configured to individually control the current flowing through the light emitting units 10 a to 10 c of the light source unit 1 a according to the control of the control unit 30. Further, each light source driving circuit 12 is configured to cause the corresponding light emitting units 10 a to 10 c to perform pulse light emission under the control of the control unit 30. Thereby, each light emitting part 10a-10c which consists of an element row | line | column of the linear LED element 11 is made into 1 unit, and lighting and light extinction are controlled for every element row | line | column.

  The switch 13 is configured to turn on and off the light emitting units 10 a to 10 c according to the control of the control unit 30. In addition, the switch 13 is configured to shift the timing of pulse light emission of the light emitting units 10 a to 10 c from each other by turning on the light emitting units 10 a to 10 c in order according to the control of the control unit 30.

  The detection unit 2 is an ultrasonic detection probe. As shown in FIG. 1, the detection unit 2 is formed to extend in the X direction while being sandwiched between a pair of light source units 1 a and 1 b arranged on both sides in the Y direction. In addition, the ultrasonic vibration element 20 of the detection unit 2 is disposed at the tip (end on the Z2 direction side) of the detection unit 2 so as to be close to the subject P. The ultrasonic vibration element 20 is configured to detect an acoustic wave (ultrasonic wave) AW and to irradiate the subject P with ultrasonic waves. The detection unit 2 (ultrasonic vibration element 20) detects the acoustic wave AW generated from the detection object Q and the ultrasonic wave reflected in the subject P, and outputs a detection signal via the signal line 30b. It is configured to transmit to the control unit 30.

  As shown in FIG. 3, the detection unit 2 has a center frequency Fmax at which the acoustic wave reception sensitivity is maximized and voltage conversion of the acoustic wave can be performed efficiently. That is, the detection unit 2 is configured to be able to detect with high sensitivity an acoustic wave having a frequency equal to the center frequency Fmax. The detection unit 2 has a detection wave frequency band B with relatively good acoustic wave detection sensitivity in the frequency bands before and after the center frequency Fmax. The detection sound wave frequency band B of the detection unit 2 is determined from the spectrum characteristics of the detection unit 2. As described above, the detection unit 2 (the ultrasonic vibration element 20) has sensitivity in a predetermined frequency band with respect to the ultrasonic wave to be detected. In the case of the example shown in FIG. 3, the detection unit 2 has a detection sound wave frequency band B of about 3 MHz or more and about 5 MHz or less with 4 MHz as a center frequency Fmax (peak). For example, the detected sound frequency band B is set in a frequency band range of −6 dB (about ½) or more with the peak value (0 dB) as a reference.

  As shown in FIG. 2, the signal processing unit 3 is configured to process a signal corresponding to the acoustic wave AW or the ultrasonic wave detected by the detection unit 2. For example, when measuring the subject P, the signal processing unit 3 is generated from the detection target Q in the subject P and is based on a signal corresponding to the acoustic wave AW or the ultrasonic wave detected by the detection unit 2. Thus, the detection object Q is specified and imaged. Further, the signal processing unit 3 is configured to display an image of the detected detection object Q on the display unit 31.

  The control unit 30 is configured to control the light source drive circuit 12 to control the light emission of the light emitting units 10a to 10c. Specifically, the signal processing unit 3 is configured to transmit a signal for controlling the timing and the amount of light emitted from the light emitting units 10a to 10c to the light source driving circuit 12 via the signal line 30a.

  As shown in FIG. 5, the control unit 30 is configured to control the three light emitting units 10 a to 10 c to emit light in order so that the three light pulses overlap each other. Specifically, the control unit 30 is configured to first generate a light pulse by causing the light emitting unit 10a to continuously emit light for a predetermined light emitting period Ta. In addition, the control unit 30 performs pulse emission of the light emitting unit 10b after Tb after a predetermined amount of light emission timing from the light emission of the light emitting unit 10a (a period from when one light emitting unit emits light until the next light emitting unit emits light). As a timing, the light emitting unit 10b is configured to continuously emit light for a predetermined light emitting period Ta to generate an optical pulse. Further, the control unit 30 uses the light emission unit 10c to emit light continuously for a predetermined light emission period Ta with a predetermined deviation amount Tb from the light emission of the light emission unit 10b as the pulse light emission timing of the light emission unit 10c. Configured to generate. The shift amount Tb is less than or equal to half the pulse width (light emission period Ta) of the light emitting units 10a to 10c.

  Further, as shown in FIGS. 6 and 7, the control unit 30 controls the light emitted from the light emitting units 10 a to 10 c when the horizontal axis is time and the vertical axis is the light intensity. The composite waveform of the pulse is configured to approximate a sine wave shape.

  The display unit 31 is configured to display an image of the detection target Q in the subject P and various screens (operation screen, notification screen, etc.) based on control by the signal processing unit 3.

  Next, the light emission control of the control unit 30 that generates a combined waveform of light pulses having a sine wave shape will be described with reference to specific waveforms.

  As shown in FIG. 6, the case where the waveforms of the light pulses P11 to P13 of the light emitting units 10a to 10c are rectangular waves will be described. The light emission period Ta is 15t. Further, the shift amount Tb is 2t. That is, the ratio of the shift amount Tb to the light emission time Ta is set to about 0.13 (= 2t / 15t). When the light pulses P11 to P13 of the light emitting units 10a to 10c are combined under this condition, a combined waveform Ps1 that approximates a sine wave shape is generated. Further, the light emission period Ta of the composite waveform Ps1 is from 15t + 2t + 2t to 19t. This 19t (light emission period Ta) is a half cycle of the combined waveform Ps1. That is, one cycle is 38t.

  If the detection unit 2 has the optical spectrum characteristics shown in FIG. 3, the acoustic wave detected by the detection unit 2 is most efficient when the light emission period 19t is a value corresponding to the center frequency of 4 MHz. The voltage is often changed. That is, by taking the reciprocal of the center frequency, the period in which the voltage is changed most efficiently is 125 ns. Therefore, the control unit 30 is configured to generate a composite waveform as t = (125/38) so that the acoustic wave is voltage-converted most efficiently.

  Next, as shown in FIG. 7, the case where the waveforms of the light pulses P21 to P23 of the light emitting units 10a to 10c are triangular waves will be described. The light emission period Ta is set to 20t. Further, the shift amount Tb is 2t. That is, the ratio of the shift amount Tb to the light emission time Ta is set to 0.10 (= 2t / 20t). When the light pulses P21 to P23 of the light emitting units 10a to 10c are combined under this condition, a combined waveform Ps2 that approximates a sine wave shape is generated.

  In the first embodiment, the following effects can be obtained.

  In the first embodiment, as described above, the control unit 30 generates a combined waveform of a plurality of optical pulses, and the frequency of the combined waveform approaches the center frequency Fmax at which the reception sensitivity of the detection unit 2 is maximized. By controlling the amount of deviation of the timing of pulse emission, the frequency of the combined waveform can be brought close to the center frequency Fmax at which the detection sensitivity of the detection unit 2 is maximized, so that it is not detected by the detection unit 2 (converted to heat). ) Laser light that becomes an acoustic wave can be prevented from being emitted from the light source unit 1a (1b). Therefore, the acoustic wave can be detected efficiently in the detection unit 2. As a result, a clear acoustic image can be obtained.

  Moreover, in 1st Embodiment, as mentioned above, the control part 30 is comprised so that the light emission parts 10a-10c may be light-emitted in order so that three light pulses may each overlap. As a result, when the three optical pulses overlap each other, the optical pulses are superimposed on each other in the vicinity of the center of the composite waveform by appropriately adjusting the shift amount, so that the composite waveform is a waveform having a peak at the center. be able to. That is, since the synthesized waveform can be approximated to a triangular wave that easily generates an acoustic wave, the detection unit 2 can detect the acoustic wave more efficiently and detect a strong acoustic wave. As a result, a clearer acoustic image can be obtained using the light source unit 1a (1b) whose frequency is uniquely determined.

  Further, in the first embodiment, as described above, the switch 13 for turning on and off the light emitting units 10a to 10c is further provided, and the light emitting unit is turned on by sequentially turning on the light emitting units 10a to 10c. The control unit 30 is configured so that the timings of pulse emission of 10a to 10c are shifted from each other. As a result, noise (electromagnetic waves) that causes image disturbance that occurs during switching of the light emitting units 10a to 10c can be dispersed, so that the noise level can be reduced. As a result, a clearer acoustic image can be obtained.

  Moreover, in 1st Embodiment, as mentioned above, the control part 30 is comprised so that the light emission parts 10a-10c may be light-emitted in order so that a synthetic | combination waveform may approximate a sine wave shape. As a result, the synthesized waveform of the acoustic wave approaches a sine wave shape, and an acoustic wave that becomes a harmonic component (for example, a frequency that is three times the fundamental frequency or a frequency that is five times the fundamental frequency) appears by frequency analysis. Thus, an acoustic wave can be generated close to a single frequency (fundamental frequency). Therefore, it is possible to suppress the emission of laser light that is an acoustic wave as a harmonic component that is not detected by the detection unit 2 (converted into heat) from the light source unit 1a (1b). As a result, an acoustic wave can be detected more efficiently in the detection unit 2, and a clearer acoustic image can be obtained.

  In the first embodiment, as described above, the deviation amount of the pulse light emission timing of the light emitting units 10a to 10c is set to be equal to or less than half the pulse width of the light pulse of the light emitting units 10a to 10c. Thereby, since the overlapping part (time) of a plurality of light pulses becomes large, the synthesized waveform can be made closer to a sine wave shape.

  Moreover, in 1st Embodiment, as mentioned above, the LED element 11 is provided in the light emission parts 10a-10c of the light source part 1a (1b). Thereby, power consumption can be reduced by using the LED element 11 with comparatively small power consumption.

(Second Embodiment)
Next, a second embodiment will be described with reference to FIGS. In the second embodiment, unlike the first embodiment in which three optical pulses are combined to generate a combined waveform, an example in which five optical pulses are combined to generate a combined waveform will be described. Note that in the first embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  As shown in FIG. 8, the photoacoustic imaging apparatus 200 according to the second embodiment includes a pair of light source units 201 a and 201 b and a control unit 230. In addition, since the light source parts 201a and 201b are comprised substantially symmetrically to the Y2 direction side and the Y1 direction side across the detection part 2, only the light source part 201a on the Y2 direction side will be described below.

  The light source unit 201a is provided with five light emitting units 210a to 210e. The light emitting units 210a to 210e are each composed of an LED element array having a plurality (21) of LED elements 11 arranged linearly in the X direction. The light emitting units 210a to 210e are arranged so that the light emitting unit 210a, the light emitting unit 210b, the light emitting unit 210c, the light emitting unit 210d, and the light emitting unit 210e are arranged in parallel from the detection unit 2 side (from the Y1 direction side). ing. The light emitting units 210a to 210e are configured to generate optical pulses having the same waveform (rectangular wave or triangular wave).

  Here, the light emission control in which the control unit 230 generates a combined waveform of optical pulses having a sine wave shape will be described with reference to specific waveforms.

  As shown in FIG. 9, the case where the waveforms of the light pulses P31 to P35 of the light emitting units 210a to 210e are triangular waves will be described. The light emission period Ta is 15t. Further, the shift amount Tb is 2t. That is, the ratio of the shift amount Tb to the light emission time Ta is set to about 0.13 (= 2t / 15t). Under these conditions, when the light pulses P31 to P35 of the light emitting units 210a to 210e are combined, a combined waveform Ps3 that approximates a sine wave shape is generated.

  Next, as shown in FIG. 10, the case where the waveforms of the light pulses P41 to P45 of the light emitting units 210a to 210e are triangular waves will be described. The light emission period Ta is set to 20t. Further, the shift amount Tb is 2t. That is, the ratio of the shift amount Tb to the light emission time Ta is set to 0.10 (= 2t / 20t). When the light pulses P41 to P45 of the light emitting units 210a to 210e are combined under this condition, a combined waveform Ps4 that approximates a sine wave shape is generated.

  Next, unlike the case shown in FIGS. 9 and 10, a case where the amount of deviation of the optical pulse is not constant will be described. Here, the case where the waveforms of the light pulses P51 to P55 of the light emitting units 210a to 210e are triangular waves will be described. Specifically, as shown in FIG. 11, the control unit 230 includes the optical pulses at both ends that are emitted first and last in the optical pulse train formed by overlapping the optical pulses P51 to P55 of the light emitting units 210a to 210e. Control is performed to shift the first shift amount Tbb between P51 and P55 and the light pulses P52 and P54 adjacent to the light pulses P51 and P55 at both ends. Further, the control unit 230 is configured to perform control to shift a second shift amount smaller than the first shift amount Tbb between the plurality of light pulses P52 to P54 sandwiched between the light pulses P51 and P55 at both ends. . As an example, the second deviation amount is set to Tbb / 2, which is half the first deviation amount Tbb.

  The light emission period Ta is set to 20t. The first deviation amount Tbb is 2t. That is, the ratio of the first shift amount Tbb to the light emission time Ta is set to 0.10 (= 2t / 20t). Accordingly, the ratio of the second shift amount to the light emission time Ta is 0.05 (= 1t / 20t). When the light pulses P51 to P55 of the light emitting units 210a to 210e are combined under this condition, a combined waveform Ps5 that approximates a sine wave shape is generated. The synthesized waveform Ps5 is steeper and has a narrower bandwidth than the synthesized waveform Ps4 shown in FIG. 10 (indicated by a two-dot chain line in FIG. 11).

  In the second embodiment, the following effects can be obtained.

  In the second embodiment, similarly to the first embodiment, the controller 230 generates a combined waveform of a plurality of optical pulses, and the frequency of the combined waveform is the center frequency Fmax at which the receiving sensitivity of the detector 2 is maximized. By controlling the amount of deviation of the pulse emission timing so as to approach the distance, a clear acoustic image can be obtained using the light source unit 201a (201b) whose frequency is uniquely determined.

  In the second embodiment, as described above, the controller 230 causes the light at both ends to be emitted first and last in the optical pulse train formed by overlapping the light pulses of the five light emitting units 210a to 210e. The first deviation amount is shifted between the pulse and the optical pulse adjacent to the optical pulses at both ends, and the second deviation amount is smaller than the first deviation amount between the plurality of optical pulses sandwiched between the optical pulses at both ends. It is configured to perform the shifting control. Thereby, compared with the optical pulse at both ends and the optical pulse adjacent to the optical pulses at both ends, a plurality of optical pulses sandwiched between the optical pulses at both ends become dense, so that the peak of the combined waveform can be made higher. Therefore, a larger acoustic wave can be detected by the detection unit 2. As a result, a clearer acoustic image can be obtained.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiment but by the scope of claims for patent, and further includes all modifications (modifications) within the meaning and scope equivalent to the scope of claims for patent.

  For example, in the said 1st and 2nd embodiment, although the light emission part showed the example containing an LED element, this invention is not limited to this. In the present invention, the light emitting unit may include a light source other than the LED element. For example, as in the modification shown in FIG. 12, the light emitting units 510a to 510c may include an organic light emitting diode element or a solid state laser. In addition, when the light emission parts 510a-510c contain an organic light emitting diode element, the photoacoustic imaging device 500 provided with the organic light emitting diode element can be easily downsized by using an organic light emitting diode element that can be easily reduced in thickness. can do. Moreover, when the light emission parts 510a-510c contain a solid-state laser, a clearer acoustic image can be obtained by using the solid-state laser which emits a laser beam with high output. Further, when the light emitting units 510a to 510c include a solid-state laser, as shown in FIG. 13, by combining a plurality of optical pulses, the optical pulses on the rectangular wave are individually brought close to a sinusoidal shape. Is possible.

  In the first and second embodiments, an example in which a synthesized waveform is generated by synthesizing three or five optical pulses has been described. However, the present invention is not limited to this. In the present invention, the combined waveform may be generated by combining two or more light pulses without being limited to three or five.

  Moreover, in the said 1st and 2nd embodiment, although the signal processing part showed the example which included a display part integrally, this invention is not limited to this. In the present invention, the signal processing unit and the display unit may be separated from each other without the signal processing unit integrally including the display unit.

  In the first and second embodiments, the example in which the amount of deviation of the pulse emission timing of the plurality of light emitting units is set to half the pulse width of the light pulse of the light emitting unit is shown, but the present invention is not limited to this. . In the present invention, the shift amount of the pulse light emission timings of the plurality of light emitting units may be smaller or larger than half the pulse width of the light pulse of the light emitting unit.

  In the first and second embodiments, the example in which the combined waveform is approximated to a sine wave shape is shown, but the present invention is not limited to this. In the present invention, the synthesized waveform may be approximated to a triangular wave shape.

DESCRIPTION OF SYMBOLS 1a, 1b, 201a, 201b Light source part 2 Detection part 10a-10c, 210a-210e, 510a-510c Light emission part 11 Light emitting diode (LED) element 13 Switch 30, 230 Control part 100, 200, 500 Photoacoustic imaging device P Subject Q Object to be detected AW Acoustic wave Tb Deviation amount Tbb First deviation amount P11 to P13, P21 to P23, P31 to P35, P41 to P45, P51 to P55 Light pulse Ps1 to Ps5 Composite waveform

Claims (10)

A light source unit including a plurality of light emitting units that emit pulses; and
A detection unit for detecting an acoustic wave generated from a detection target in a subject that has absorbed light emitted from the light emitting unit; and
By shifting the pulse emission timings of the plurality of light emitting units from each other, the plurality of light emitting units sequentially emit light so that the light pulses of the plurality of light emitting units overlap each other, thereby causing the plurality of light pulses of the plurality of light emitting units to emit light. And a control unit that controls the amount of deviation of the timing of the pulse emission so that the frequency of the combined waveform approaches the frequency at which the reception sensitivity of the detection unit is maximized. apparatus.   The photoacoustic imaging apparatus according to claim 1, wherein the control unit is configured to perform control to sequentially emit the plurality of light emitting units so that three or more light pulses overlap each other.   The photoacoustic imaging apparatus according to claim 2, wherein the control unit is configured to perform control so that the plurality of light emitting units emit light in order so that odd and three or more light pulses overlap each other. A switch for turning on and off the plurality of light emitting units;
The said control part is comprised so that the timing of the pulse light emission of these light emission parts may mutually be shifted by turning on the said switch so that it may light-emit these light emission parts in order. 4. The photoacoustic imaging apparatus according to any one of items 3. Four or more light pulses of the light emitting unit are provided,
The control unit includes: an optical pulse at both ends of the optical pulse train formed by overlapping the optical pulses of the four or more light emitting units; and an optical pulse adjacent to the optical pulses at the both ends. The first shift amount is shifted between the first and second optical pulses, and the second shift amount smaller than the first shift amount is shifted between the plurality of optical pulses sandwiched between the light pulses at both ends. The photoacoustic imaging apparatus of any one of Claims 1-4.   6. The control unit according to claim 1, wherein the control unit is configured to perform control so that the plurality of light emitting units emit light in order so that the combined waveform approaches a sine wave shape. Photoacoustic imaging device.   The photoacoustic imaging apparatus according to claim 6, wherein a deviation amount of pulse emission timings of the plurality of light emitting units is equal to or less than a half of a pulse width of an optical pulse of the light emitting unit.   The photoacoustic imaging apparatus according to claim 1, wherein the light emitting unit of the light source unit includes a light emitting diode element.   The photoacoustic imaging apparatus according to claim 1, wherein the light emitting unit of the light source unit includes an organic light emitting diode element. The photoacoustic imaging apparatus according to claim 1, wherein the light emitting unit of the light source unit includes a solid-state laser.

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