Quantitation of near infrared spectroscopic data in a scattering medium such as tissue requires knowledge of the optical pathlength in the medium. This can now be estimated directly from the time of flight of picosecond length light pulses. Monte Carlo modelling of light pulses in tissue has shown that the mean value of the time dispersed light pulse correlates with the pathlength used in quantitative spectroscopic calculations. This result has been verified in a phantom material. Time of flight measurements of pathlength across the rat head give a pathlength of 5.3+or-0.3 times the head diameter.

http://iopscience.iop.org/article/10.1088/0031-9155/33/12/008/pdf

Estimation of optical pathlength through tissue from direct time of flight measurement

Digital holography is an emerging field of new paradigm in general imaging applications. We present a review of a subset of the research and development activities in digital holography, with emphasis on microscopy techniques and applications. First, the basic results from the general theory of holography, based on the scalar diffraction theory, are summarized, and a general description of the digital holographic microscopy process is given, including quantitative phase microscopy. Several numerical diffraction methods are described and compared, and a number of representative configurations used in digital holography are described, including off-axis Fresnel, Fourier, image plane, in-line, Gabor, and phase-shifting digital holographies. Then we survey numerical techniques that give rise to unique capabilities of digital holography, including suppression of dc and twin image terms, pixel resolution control, optical phase unwrapping, aberration compensation, and others. A survey is also given of representative application areas, including biomedical microscopy, particle field holography, micrometrology, and holographic tomography, as well as some of the special techniques, such as holography of total internal reflection, optical scanning holography, digital interference holography, and heterodyne holography. The review is intended for students and new researchers interested in developing new techniques and exploring new applications of digital holography.

/pdf/principles-and-techniques-of-digital-holographic-microscopy-56tmwltigo.pdf

Principles and techniques of digital holographic microscopy

A laser catheter is disclosed wherein optical fibers carrying laser light are mounted in a catheter for insertion into an artery to provide controlled delivery of a laser beam for percutaneous intravascular laser treatment of atherosclerotic disease. A transparent protective shield is provided at the distal end of the catheter for mechanically diplacing intravascular blood and protecting the fibers from the intravascular contents, as well as protecting the patient in the event of failure of the fiber optics. Multiple optical fibers allow the selection of tissue that is to be removed. A computer controlled system automatically aligns fibers with the laser and controls exposure time. Spectroscopic diagnostics determine what tissue is to be removed.

Catheter for laser angiosurgery

Laser energy produced by a laser operating in the mid-infrared region (approximately 2 micrometers) is delivered by an optical fiber in a catheter to a surgical site for biological tissue removal and repair. Disclosed laser sources which have an output wavelength in this region include: Holmium-doped Yttrium Aluminum Garnet (Ho:YAG), Holmium-doped Yttrium Lithium Fluoride (Ho:YLF), Erbium-doped YAG, Erbium-doped YLF and Thulium-doped YAG. For tissue removal, the lasers are operated with relatively long pulses at energy levels of approximately 1 joule per pulse. For tissue repair, the lasers are operated in a continuous wave mode at low power. Laser output energy is applied to a silica-based optical fiber which has been specially purified to reduce the hydroxyl-ion concentration to a low level. The catheter may be comprised of a single optical fiber or a plurality of optical fibers arranged to give overlapping output patterns for large area coverage.

Infrared laser catheter system

Systems and methods for the multispectral imaging of skin tissue enables automatic characterization of the condition of a region of interest of the skin, based on direct digital imaging of the region of interest (Figures 1a and 2) or the digitization of color photographic slides of the region of interest, illuminated by appropriately filtered light. Preferably, a digital image at a low spectral band is automatically segmented and that segmented mask is used to segment the other images by a digital processor (Figure 3b). Parameters are estimated through wavelet maxima representation. Parameters related to the texture, asymmetry, blotchines and border irregularities are also automatically estimated (Figure 11). The region of interest is automatically characterized by the digital processor, based on those parameters. The region of interest may include a skin lesion, in which case the present invention enables the characterization of the lesion as malignant or benign (Figures 4a and 4b). The region of interest may also include wounds or burns.

Systems and methods for the multispectral imaging and characterization of skin tissue

Cancer diagnosis device contains an endoscope comprising a light pipe used to transmit light beams from respective light sources and an image guide used to observe the flesh of the organism during both diagnosis and treatment. The tip of the endoscope faces toward the focuses where a photosensitive material having an affinity to the focuses of cancer has been absorbed so that a treatment for cancer can be performed by exposing the organism affected by cancer to the laser beam. The attainable the laser beam within a focus is thus increased by the use of the laser beam pulse from a first laser beam pulse source. In addition to the above, the cancer diagnosis device contains a second laser beam pulse source used to transmit a light beam to the focuses through the light pipe for making a diagnosis, a selector used to selectively pick up the light beam from the first laser beam pulse source or the second laser beam pulse source, a spectroscope used to obtain the spectral response from emission of light led through the image guide used for observation from the flesh of the organism where fluorescence occurs, an imaging device used to pick up the spectral response, a graphic display used to graphically display the processed spectra picked up by the imaging device, and a controller used to control emission of light from the second laser beam pulse source and also to make the operation of the imaging device synchronize with the second laser beam pulse source.

Cancer diagnosis device utilizing laser beam pulses

The experimental demonstration of a broad-area Quasi-continuous-wave (QCW) laser-diode array pumped cesium vapor laser is reported in this letter according to our experimental results. We used a volume-Bragg grating to narrow the spectral linewidth for acquirement of enough resonance transitions. A glass cylindrical cell filled with cesium/buffer gas was set in an end-pumped flat-concave cavity and the gas pressure was set lower than 1atm. Using the QCW drive mode with the repetitive rate and pulse width of 1kHz and 50μs, respectively, 13.45μJ pulse energy has been achieved with the slope efficiency of about ∼1.8%.

Cesium vapor laser pumped by a volume-Bragg-grating coupled quasi-continuous-wave laser-diode array

Device for diagnosing cancers

β-FeSi2/Si light-emitting devices were prepared by growing continuous and highly oriented β-FeSi2 films on Si (111) substrates using RF magnetron-sputtering deposition with a Fe target. In-plane X-ray diffraction reveals that the epitaxial relationship is such that β-FeSi2 // Si, indicating a (110) orientation in the growth direction. Post annealing was performed at 830°C and Al electrodes were deposited on both p-β-FeSi2 and n-Si sides. Room-temperature 1.56 µm electroluminescence was clearly observed from such a simple structure for the first time. Compared with the previously reported results for β-FeSi2 balls or β-FeSi2 precipitates buried in Si, the injection current density is more than one order of magnitude lower, indicating that the nonradiative recombination was effectively suppressed for the junction consisting of a continuous film.

http://iopscience.iop.org/article/10.1143/JJAP.41.L1200/pdf

Teruo Hiruma

Papers

Cancer diagnosis device utilizing laser beam pulses

Cesium vapor laser pumped by a volume-Bragg-grating coupled quasi-continuous-wave laser-diode array

Device for diagnosing cancers

Room-Temperature 1.56 µm Electroluminescence of Highly Oriented β-FeSi2/Si Single Heterojunction Prepared by Magnetron-Sputtering Deposition

Approaches of output improvement for a cesium vapor laser pumped by a volume-Bragg-grating coupled laser-diode-array