We present three-dimensional (3-D) in vivo photoacoustic (PA) images of the blood vasculature of a chicken chorioallantoic membrane (CAM) obtained by using a fiber-based noncontact PA tomography system. With a fiber-optic heterodyne interferometer, the system measures the surface displacement of a sample, induced by the PA wave, which overcomes the disadvantage of physical-contact of ultrasonic transducer in a conventional system. The performance of an implemented system is analyzed and its capability of in vivo 3-D bioimaging is presented. At a depth of 2.5 mm in a phantom experiment, the lateral and axial resolutions were measured as 100 and 30 μm, respectively. The lateral resolution became doubled at a depth of 7.0 mm; however, interestingly, the axial resolution was not noticeably deteriorated with the depth. With the CAM experiment, performed under the American National Standards Institute laser safety standard condition, blood vessel structures placed as deep as 3.5 mm were clearly recognized.
We present a fiber-based dual-modal imaging system that combines non-contact photoacoustic tomography (NCPAT) and fluorescence imaging by using double cladding fiber (DCF). The NCPAT system utilizing an all-fiber heterodyne interferometer as an ultrasound detector measures the photoacoustic signal at the sample surface without physical contact. Fluorescence imaging system is composed of fiber-optics to deliver the excitation light and the emission light. For combined system the probe consists of a specially fabricated DCF coupler and a lensed fiber so that we can simultaneously acquire the signals of two systems with the same probe. The DCF has a core and two claddings, inner and outer, which allows two concentric light-guiding channels via the core and the inner cladding. The lensed fiber of the DCF probe is compactly fabricated to focus the interferometer light and the excitation light, and to efficiently collect the fluorescence signal. To demonstrate the feasibility of the proposed dual-modal system, we have conducted phantom experiments using tissue mimicking phantoms which contained a couple of tubes filled with fluorescein solution and black ink, respectively. The proposed imaging system is implanted with fiber-optic configurations so that it has the potential for minimally invasive and improved diagnosis and guided treatment of diseases.
We report an all-fiber heterodyne interferometer for the measurements of laser-induced thermoelastic deformation to estimate the Gruneisen coefficient and the optical attenuation depth of a sample. The system comprises a Q-switched Nd-YAG laser providing a nanosecond excitation pulse and an all-fiber heterodyne interferometer that measures the induced displacement of the sample surface. To evaluate the system, phantom experiments were carried out with various gelatin-based models. The results show that the attenuation depth and Gruneisen coefficient of the phantoms were about 4.256 mm and 0.568, respectively. In addition, increase of the weight fraction of gelatin led increase in the Gruneisen coefficient.
We propose the noncontact photoacoustic tomography system that reads the acoustic signal by using an optical fiberbased heterodyne interferometer. The surface displacement of a specimen, resulting from the acoustic wave generated by irradiation of a laser pulse and its absorption inside the specimen, is optically measured by the heterodyne interferometer. With the data set of the surface displacement, the photoacoustic image of the specimen is reconstructed by a Fourier transform based reconstruction algorithm. This proposed method is experimentally evaluated by using a phantom sample that contains PET fibers.
A fiber optic sensor based on the wavelength division multiplexer coated with a palladium (Pd) thin film is designed for
hydrogen gas detection. The sensing mechanism of this sensor is measuring the wavelength shift that is induced by the
evanescent field interaction with the refractive index change of Pd film when it absorbs hydrogen.
An optical interferometric system for the simultaneous measurements of physical thickness and refractive group index is
implemented. The proposed system is based on a spectral-domain optical low coherence interferometry with two sample
probes facing to each other. The two-probe approach enables simultaneous measurements of thickness and group index
of a transparent sample. The average measurement errors were ~0.112 % in the physical thickness and ~0.035 % in the
group index, respectively.
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