Photoacoustic measuring apparatus

1 . A photoacoustic measuring apparatus comprising:

a light source configured to emit laser of a predetermined wavelength to a measurement target;

a photoacoustic detector configured to detect a photoacoustic signal generated from the measurement target receiving the laser light emitted from the light source;

a contact sensor including a first bioimpedance electrode and a second bioimpedance electrode, the contact sensor being configured to acquire a bioimpedance value when the electrodes are placed in contact with the measurement target and an operator during use of the photoacoustic measuring apparatus; and

a controller configured to decide whether the operator and the measurement target are the same individual, based on the bioimpedance value measured between the first bioimpedance electrode and the second bioimpedance electrode.

2 . The photoacoustic measuring apparatus of claim 1 , wherein the photoacoustic detector includes an ultrasonic sensor configured to detect a photoacoustic wave generated in a photoacoustic wave generating area in the measurement target in a predetermined frequency band,

wherein with a light-incident position and a beam width of the laser light, a center of the photoacoustic wave generating area, and a position of the ultrasonic sensor given according to a predetermined geometry, the frequency band of the ultrasonic sensor is configured to include a frequency corresponding to a wavelength equal to twice the beam width at the point of light incidence.

3 . The photoacoustic measuring apparatus of claim 2 , wherein the frequency band of the ultrasonic sensor is configured to include a frequency corresponding to a wavelength equivalent to a distance from the photoacoustic wave generating area to the ultrasonic sensor according to the predetermined geometry.

4 . The photoacoustic measuring apparatus of claim 2 , wherein the pulse width of the laser light is determined such that twice the time difference between a maximum pressure time and a minimum pressure time of a heat pressure wave estimated in the measurement target by the laser pulse energy is included within a period range corresponding to the frequency band of the ultrasonic sensor.

5 . The photoacoustic measuring apparatus of claim 2 , wherein the laser light has a beam cross-section having a fast axis and a slow axis, and the fast axis is aligned to face the ultrasonic sensor.

6 . The photoacoustic measuring apparatus of claim 5 , further comprising a sampling unit configured to sample a waveform of the detected photoacoustic wave at a predetermined sampling rate to obtain sampling data,

wherein the sampling rate is determined based on a photoacoustic frequency corresponding a wavelength that is twice the beam width along the fast axis of the beam cross section.

7 . The photoacoustic measuring apparatus of claim 6 , wherein the sampling data is obtained by repeatedly performing a procedure for N frames, wherein N is a natural number of 2 or larger, wherein the procedure of each of the N frames is composed of an operation of emitting the laser light to the measurement target, an operation of detecting the photoacoustic wave generated in the photoacoustic wave generating area in the measurement target in the predetermined frequency band, and an operation of sampling a waveform of the photoacoustic wave at a predetermined sampling rate, wherein N pieces of the sampling data respectively obtained in the N frames are coherent-averaged.

8 . The photoacoustic measuring apparatus of claim 2 , wherein the frequency band of the ultrasonic sensor is determined to include a frequency at which a magnitude of a proximity effect between the photoacoustic wave generating area and the ultrasonic sensor is smaller than or equal to a predetermined reference value.

9 . The photoacoustic measuring apparatus of claim 2 , wherein a center frequency of the frequency band of the ultrasonic sensor is determined based on a frequency corresponding to a wavelength equivalent to a distance from a center of the photoacoustic wave generating area to a center of the measurement surface of the ultrasonic sensor.

10 . The photoacoustic measuring apparatus of claim 1 , wherein the photoacoustic detector includes an ultrasonic sensor configured to detect a photoacoustic wave generated in the photoacoustic wave generating area in the measurement target in a predetermined frequency band,

wherein a distance between the photoacoustic wave generating area and the ultrasonic sensor is determined based on a wavelength corresponding to a frequency within the frequency band of the ultrasonic sensor.

11 . The photoacoustic measuring apparatus of claim 10 , wherein a beam width of the laser light is determined based on half a wavelength length of a maximum frequency within the frequency band of the ultrasonic sensor.

12 . The photoacoustic measuring apparatus of claim 10 , wherein a pulse width of the laser light is determined such that twice the time difference between a maximum pressure time and a minimum pressure time of a heat pressure wave estimated in the measurement target by the laser pulse energy is included within a period range corresponding to the frequency band of the ultrasonic sensor.

13 . The photoacoustic measuring apparatus of claim 10 , wherein the laser light has a beam cross-section having a fast axis and a slow axis, and the fast axis is aligned to face the ultrasonic sensor.

14 . The photoacoustic measuring apparatus of claim 13 , wherein a beam width of the slow axis of the beam cross-section of the laser light is determined based on half a wavelength length of a maximum frequency of the frequency band of the ultrasonic sensor.

15 . The photoacoustic measuring apparatus of claim 10 , wherein a distance between the photoacoustic wave generating area and the ultrasonic sensor is determined based on a distance at which a proximity effect due to a wavelength belonging to the frequency band of the ultrasonic sensor is smaller than or equal to a predetermined reference value.

16 . The photoacoustic measuring apparatus of claim 10 , wherein a distance from a center of the photoacoustic wave generating area to a center of a measurement surface of the ultrasonic sensor is determined based on a wavelength corresponding to a center frequency of the frequency band of the ultrasonic sensor.

17 . The photoacoustic measuring apparatus of claim 10 , further comprising a sampling unit configured to sample a waveform of the detected photoacoustic wave at a predetermined sampling rate to obtain sampling data,

wherein the sampling data is obtained by repeatedly performing a procedure for N frames, wherein N is a natural number of 2 or larger, wherein the procedure of each of the N frames is composed of an operation of emitting the laser light to the measurement target, an operation of detecting the photoacoustic wave generated in the photoacoustic wave generating area in the measurement target in the predetermined frequency band, and an operation of sampling a waveform of the photoacoustic wave at a predetermined sampling rate,

wherein N pieces of the sampling data respectively obtained in the N frames are coherent-averaged.