Photoacoustic measurement apparatus
Disclosed is a photoacoustic measurement apparatus that irradiates a light beam onto a subject, from a same side as that of an acoustic wave detector, and that measures photoacoustic waves. The photoacoustic measurement apparatus has: an acoustic wave detector; a diffraction grating member provided in front of a detection surface of the detector; a light source that generates a light beam; and an optical system that guides the light beam from the light source towards the diffraction grating member. The diffraction grating member is configured such that the light beam led to the diffraction grating member is outputted by the diffraction grating member towards a subject surface that opposes the detection surface of the detector. As a result, light beams can strike a biological body in a near-perpendicular angle. This affords greater illumination efficiency, and allows light of substantial light energy to be irradiated deep inside biological structures.
1. A photoacoustic measurement apparatus that irradiates a subject with a light beam, from a same side as that of an acoustic wave detector, and that measures photoacoustic waves, the apparatus comprising:
an acoustic wave detector;
a diffraction grating member provided in front of a detection surface of said acoustic wave detector;
a light source that generates a light beam; and
an optical system that guides the light beam from said light source towards said diffraction grating member,
wherein said diffraction grating member is configured such that the light beam led to said diffraction grating member is outputted by said diffraction grating member towards a subject surface that opposes said detection surface of said acoustic wave detector,
wherein the shape of said detection surface is rectangular or circular, and
wherein said diffraction grating member is configured such that an incidence angle θ of the light beam outputted by said diffraction grating member with respect to the subject satisfies tan θ<L/2d,
where L denotes a length of a short side or diameter of said detection surface, and d denotes a distance between said detection surface and a surface of contact with the subject.
2. The photoacoustic measurement apparatus according to claim 1 , wherein said diffraction grating member is configured such that the light beam outputted by said diffraction grating member is perpendicular to said detection surface.
3. The photoacoustic measurement apparatus according to claim 1 , wherein
an incidence angle of the light beam that strikes said diffraction grating member varies in accordance with positions, and
a structure of said diffraction grating member varies in accordance with the incidence angle of the light beam, with diffracted light outputted by said diffraction grating member being perpendicular to said detection surface of said acoustic wave detector.
4. The photoacoustic measurement apparatus according to claim 1 , wherein said diffraction grating member is transmissive to acoustic waves.
5. The photoacoustic measurement apparatus according to claim 1 , further comprising a flat plate that is disposed between said acoustic wave detector and the subject, and that compresses the subject parallelly to said detection surface of said acoustic wave detector,
wherein said flat plate is said diffraction grating member.