Acoustic wave detection probe and photoacoustic measurement apparatus provided with the same

1. An acoustic wave detection probe provided with a light guide section, and an acoustic wave transducer, wherein the light guide section comprises:

a homogenizer that flat-tops an energy profile of high energy measuring light entered the light guide section;

a light condensing member that condenses the high energy measuring light transmitted through the homogenizer; and

a bundle fiber which includes a plurality of optical fibers and is disposed such that the high energy measuring light transmitted through the light condensing member enters from an entrance end of the bundle fiber, wherein

the homogenizer further diffuses the high energy measuring light;

when the focal length of the light condensing member, the spread angle of the high energy measuring light when entering the homogenizer, and the diffusion angle of the homogenizer are taken as f, φ, and θ respectively, the light condensing member condenses the high energy measuring light such that a minimum beam diameter D defined by Formula 1 below satisfies Formula 2 below in relation to a diameter d of the bundle fiber; and the bundle fiber is disposed such that the high energy measuring light enters the bundle fiber with the beam diameter D being 0.8 d to 1.2 d;

D

=

2.5

·

f

·

tan

⁡

(

(

ϕ

2

)

2

+

(

θ

2

)

2

)

Formula

⁢

⁢

1

0.8

⁢

⁢

d

≦

D

≦

1.2

⁢

⁢

d

Formula

⁢

⁢

2

the light guide section comprises a beam expander optical system immediately before the entrance side of the homogenizer, the beam expander optical system having an expansion factor that conforms to angular apertures of the plurality of optical fibers so that the high energy measuring light is expanded to a beam diameter that conforms to the angular apertures of the plurality of optical fibers;

the homogenizer is a light shaping diffuser in which small lenses are disposed randomly on one side of a substrate;

the light guide section guides the high energy measuring light such that the high energy measuring light is outputted toward a subject and the acoustic wave transducer detects a photoacoustic wave generated in the subject by the proiection of the high energy measuring light; and

the minimum beam diameter D is set to inhibit damage to the bundle fiber and eliminate the imbalance in the amount of energy between each light traveling through each optical fiber of the bundle fiber.

2. The probe as claimed in claim 1 , wherein the entrance end of the bundle fiber is fusion processed.

3. The probe as claimed in claim 1 , wherein the outer circumferences of the plurality of optical fibers are covered with a material having high durability against optical energy at the entrance end.

4. The probe as claimed in claim 3 , wherein the material having high durability against optical energy is silica.

5. The probe as claimed in claim 1 , wherein exit ends of optical fibers in each of a plurality of divided areas divided in an end face arrangement of the entrance end are disposed according to a relative magnitude with respect to each divided area to which the exit ends belong such that an energy profile when the high energy measuring light exits from the exit ends of all optical fibers becomes homogeneous as a whole.

6. The probe as claimed in claim 5 , wherein the plurality of divided areas is divided according to the distance from the center of the bundle fiber.

7. The probe as claimed in claim 1 , wherein the light guide section comprises at least one light guide plate having a connection surface to which at least some of the exit ends of the plurality of optical fibers are connected and an exit surface from which the high energy measuring light entered from the connection surface exits.

8. The probe as claimed in claim 7 , wherein the light guide plate is provided in plurality and disposed across the acoustic wave transducer.

9. The probe as claimed in claim 1 , wherein the probe comprises a holding section that holds the entrance end so as to cover the entrance face of the bundle fiber and has a window section at a portion where the high energy measuring light enters.

10. The probe as claimed in claim 9 , wherein the window section comprises an ND filter.

11. A photoacoustic measurement apparatus, comprising:

the probe of claim 1 ; and

a signal processor that processes a photoacoustic signal of the photoacoustic wave detected by the acoustic wave transducer.

12. The photoacoustic measurement apparatus as claimed in claim 11 , wherein the apparatus comprises:

a light source that outputs the high energy measuring light;

an equipment housing having a mounting section optically connected to the light source and holding the homogenizer; and

a holding section that integrally holds the light condensing member and the bundle fiber,

wherein the mounting section and the holding section have connector structures removably attachable to each other.

13. The photoacoustic measurement apparatus as claimed in claim 11 , wherein the apparatus comprises:

a light source that outputs the high enemy measuring light;

an equipment housing having a mounting section optically connected to the light source and holding the homogenizer and the light condensing member; and

a holding section that holds the entrance end so as to cover the entrance face of the bundle fiber and has a window section at a portion where the high enemy measuring light enters,

wherein the mounting section and the holding section have connector structures removably attachable to each other.

14. The photoacoustic measurement apparatus as claimed in claim 11 , wherein the signal processor comprises an acoustic image generator that generates a photoacoustic image based on the photoacoustic signal.

15. The photoacoustic measurement apparatus as claimed in claim 14 , wherein:

the acoustic wave transducer detects a reflected acoustic wave of a transmitted acoustic wave to the subject; and

the acoustic image generator generates a reflected acoustic wave image based on a signal of the reflected acoustic wave.