We present a new detection scheme for acousto-optic tomography, based on pseudo-random modulation of the utlrasound and illumination combined with hterodyne parallel speckle detection. This setup allows to perform tomographies inside several centimeter-thick scattering sample. Test experiments confirm the suitability of this method to perform tomographies inside various types of optically scattering media.

Thermoacoustic computed tomography (TACT) is a method to visualize structures with optical contrast hidden in a light-scattering medium. Pulses of electromagnetic radiation that are absorbed in an optically heterogeneous object cause a distribution of energy density and thermoelastic pressure that is determined by the distribution of optical absorption. In conventional TACT, pressure waves emitted by the object are measured with small acoustic detectors and the temporal signals are used for reconstruction of the energy density distribution. To avoid the limitation of the spatial resolution of the image by the finite detector size we propose to use large, integrating detectors, where the object is always in the detector near field. This has the advantage that not only the finite size effect can be avoided but also that for image reconstruction the conventional, inverse Radon transform can be applied. In the present work the integrating detectors have the shape of a line, formed by a laser beam that is part of a Mach-Zehnder interferometer. By scanning the line detector and rotating the sample a data set can be acquired from which a full three-dimensional image of the energy density distribution in the object can be reconstructed. The data acquisition and image reconstruction procedures are described in detail. In a first imaging experiment a three-dimensional image of a phantom is presented. Finally, ways to improve the imaging speed as well as the spatial resolution are discussed.

Thermoacoustic (optoacoustic, photoacoustic) tomography is an emerging technology for imaging semitransparent objects, like soft biological tissue. Thermoacoustics combines the advantages of pure optical imaging with those of ultrasound imaging. In optical imaging the contrast is usually high, but the image resolution is poor because of the diffuse nature of light propagation. In ultrasonic imaging, the contrast between structures with similar acoustic properties (e.g. different soft tissue constituents) is low, but the spatial resolution is high because of the relatively unhindered propagation of ultrasonic waves. Due to the conversion of absorbed electromagnetic radiation into sound waves, thermoacoustics is able to generate images that at the same time have optical contrast and ultrasonic resolution. A novel measurement setup using integrating detectors is proposed and demonstrated by reconstructing the cross section of a grape. The use of integrating detectors to obtain time-retarded projections of optical absorption along surfaces parallel to the detector surface is quite different to current approaches and has important advantages. It avoids the problem of piezoelectric detectors to obtain adequate detection sensitivity when using the acoustically small element sizes required for "conventional" imaging reconstruction algorithms. Another advantage is that the reconstruction can be achieved via the inverse Radon Transform. Thus, many of the existing reconstruction methods (e.g. those using sparse data sets) developed for computerized tomography are directly applicable enabling the progress in this area to be rapid and integrating detectors may become widely adopted.

An apparatus for minimally-invasive in vivo measurements of the ciliary beat frequency (CBF) has been developed. The instrument is based on speckle interferometry technique. Since the diagnostic standard is still based on ex vivo motility analysis of cilia, a less invasive analytical technique for in vivo measurement of the CBF are thus eagerly awaited since a long time. The contrast and the resolution of conventional endoscopy are entirely insufficient for direct observation of the ciliary activity. Because of it we exploited the formation of speckle pattern. Until now, all attempts to measure CBF in vivo by laser light scattering employed a single detector, selecting an area of roughly one speckle from the speckle field. With such a detector there is no way to distinguish fluctuations on the basis of translation from the oscillations due to ciliary beat. We employed image fiber bundle with a position sensitive CCD detector, which allows detecting the motion and correcting for the motion artifacts. The biggest challenge was to combine dynamic speckle interferometry with endoscopic imaging techniques. Two approaches for merging speckle interferometry with fiber-optic endoscopy are presented. In a first, incoherent approach, the speckle image is formed on the front face of the image bundle. In a second, coherent approach, the speckles are formed after the fiber transmission by superposing the light-fields from a number of fibers by image defocusing.

The three dimensional endoscope by compound optics is presented. The system consists of a micro-lens array, a signal separator and a photo-detector array. Digital processing of the captured multiple images is used to extract the surface profile. Preliminary experiments were executed on an evaluation system to verify the principles of the system and to clarify the issues related to its implementation.

We present an imaging system which could be used for endoscopic topography. Indeed it allows for two dimensional information transmission through a unidimensional imaging channel which is a monomode optical fiber. The principle is the coupling of wavelength multiplexing and spectral interferometry and a special configuration renders this system dispersion self compensated what enables a high signal stability. Principles will be presented as well as results and limits of the system

In contrast to intensity-based fluorescence microscopy, fluorescence lifetime imaging microscopy (FLIM) bases image contrast on fluorophore excited-state lifetime. This technique is sensitive to the fluorophore's local environment (temperature, ion concentration, dissolved gas concentration, and molecular associations), while being independent of factors impacting fluorescence intensity (fluorophore concentration, photobleaching, scattering, and absorption). We present design features of a novel UV-visible-NIR wide-field time-domain FLIM system with optical sectioning (10 μm), high temporal discrimination (50 ps), and large temporal dynamic range (750 ps - 1 μs), and apply the system to probe cellular metabolic function and detect molecular activity in vivo.

We report real-time (video-rate) fluorescence lifetime imaging and its application to tissue autofluorescence and endoscopy, demonstrating FLIM of unstained ex vivo tissue at update rates of 5.5Hz through a flexible endoscope.

We report on the development of a simple technique for obtaining time-domain information using dc detection of fluorescence. We show that this is feasible for assays where a change in lifetime of an indicator occurs in reaction to an analyte, in fluorescence resonance energy transfer for example, and could be particularly useful for assays performed in the scaled-down environment of a "lab-on-a-chip". A rate equation model is presented which allows an objective analysis of the relative importance of the key measurement parameters: optical saturation of the fluorophore and excitation pulse characteristics. We present a comparison of the model with a cuvette based analysis of a carbocyanine dye where the excitation source is a 650 nm wavelength, self-pulsing AlGaInP laser diode.

Using Fourier phase microscopy, the motility of epithelial cancer cells has been quantified. The mean squared displacement analysis suggest that the cell motion is superdiffusive for cells at various stages of their life cycle.

Using Hilbert phase microscopy, a technique recently developed in our laboratory, the nanometer level structure and dynamics associated with live red blood cells have been quantified on the 10 millisecond time scale.

Based on an original numerical reconstruction algorithm (E. Cuche et al. Appl. Opt. 38, 6994 1999), we have developed a Digital Holographic Microscope (DHM), in a transmission mode, allowing to investigate noninvasively cellular structures and dynamics. DHM images of living cells in culture are presented. They represent the distribution of the optical path length over the cell, which contains information concerning both the cellular morphometry and the intracellular refractive index, and which has been measured with a sub-wavelength accuracy.

The ability of digital holographic microscopy (DHM) to provide both amplitude and phase images of a specimen makes it a convenient tool for cells analysis and recognition. Practical applications are demonstrated on pollen particles.

We present a study based on simulations describing how shot noise, an intrinsic part of the recording process with a digital camera, influences the quality of the reconstructed phase images under different beams intensities configurations.

In this presentation a model of human eye based on bimorph flexible mirror is introduced. We demonstrate experimental data of reproducing low- and high-order aberrations typical for human eye with RMS error about 5%. The presented temporal spectra of measured human eye aberrations have the main power within the range of 10 Hz. We discuss the possibility to reproduce it with our eye model. We show invalidity for the ophthalmic calibration purposes to use analytical equation based on thin lens formula. We show that proper analytical equation suitable for calibration should have dependence on the square of the distance increment and we illustrate this both by experiment and by Zemax Ray tracing modeling.

In this presentation we report our results of investigation of anisoplanatism effect in human eye. We measured aberrations of human eye depending on the location of beacon source on the retina and determined the value of the isoplanatic patch. We show that the size of isoplanatic patch depends on the direction of compensation and determine an optimal direction for every patient. To enhance quality of retina image correction we introduce lamellar eye model where aberrations of human eye are considered to be induced in two thin phase screens corresponding to cornea and crystal lens locations. For that model we found the optimal corrector location which differs from the one for the one-layer eye model.

In numerous medical and scientific fields, knowledge of the optical properties of tissues can be applied. Among many different ways of determining the optical properties of turbid media; integrating sphere measurements are widely used. However, this technique is associated with bulky equipment, complicated measuring techniques, interference compensation techniques, and inconvenient sample handling. This paper describes measurements of the optical properties of porcine brain tissue using novel instrumentation for simultaneous absorption and scattering characterization of small turbid samples. The system used measures both angularly and spatially resolved transmission and reflection and is called Combined Angular and Spatially-resolved Head (CASH) sensor. The results compare very well with data obtained with an integrating sphere for well-defined samples. The instrument was shown to be accurate to within 12% for μ_a, and 1% for μ_s' in measurements of intralipid-ink samples. The corresponding variations of data were 17%, and 2%, respectively. The reduced scattering coefficient for porcine white matter was measured to be 100 cm^-1, while the value for coagulated brain tissue was 65 cm^-1. The corresponding absorption coefficients were 2 and 3 cm^-1, respectively.

A new technique for the investigation of microvascular tissue blood concentration is presented, based on the method of polarisation spectroscopy of blood in superficial skin tissue. Linearly polarised light incident on the skin is partly reflected by the surface layers, and partly backscattered from the dermal tissue. Use of orthogonal polarisation filters over both a light source and a CCD suppresses the reflections from the surface, and only the depolarised light backscattered from the dermal matrix reaches the CCD array. By separating the colour planes of an image acquired in this manner and applying a dedicated image processing algorithm, spectroscopic information about the amount of red blood cells (RBCs) in the underlying area of tissue can be discovered. The algorithm incorporates theory that utilises the differences in light absorption of RBCs and dermal tissue in the red and green wavelength regions. In vitro fluid models compare well to computer simulations in describing a linear relationship between output signal (called TiVi_index) and RBC concentration in the physiological range of 0%-4%. In vivo evaluation of the technique via transepidermal application of acetylcholine by iontophoresis displayed a heterogeneity pattern of vasodilation, which is typical of the vasoactive agent. Extension of the technique to capture and process continuous real-time data creates a new possibility of online real-time image processing. Application of tissue viability (TiVi) imaging include skin care products and drug development, as well as investigations of microvascular angiogenesis.

Diffusion coefficients in the human sensorimotor and visual cortices were measured using diffusing-wave spectroscopy. Motor and visual activation leads to increases of the diffusion coefficients in the respective cortical areas over the values at rest.

We study DOT using 2-dimensional continuous-wave source-detector arrays on the surface of semi-infinite medium, aiming at imaging the perfusion and the hemoglobin oxygen saturation variation of the human cerebral cortex with the brain activation. We had been formulating the inverse problem with the Moore-Penrose inversion. When we use simple regularization in the inverse problem, the reconstruction sensitivity decreases markedly with the depth so that the signal in the deep range may be masked by the unwanted signal in the shallow range. In this report, we propose a reconstruction of a depth-adaptive regularization scheme, in which we assign the smaller regularization parameter with the depth. We demonstrate the improvement of the 3-dimensional reconstruction uniformity using proposed scheme.

Optical diagnostics in biological materials are hindered by fluorescence and scattering. We have developed a multimodal, multiplex, coded-aperture Raman spectrometer to detect alcohol in a lipid tissue phantom solution.

THz-technology provides new ground for label-free detection of biomolecules by taking advantage of existing hybridization techniques. Recent developments for label-free analysis of genetic material with femtomol-sensitivity using integrated functionalized THz sensors are presented. In comparison to former planar strip line approaches, the modular concept based on parallel-plate waveguides presented here provides a cost-efficient solution given the exchangeability, disposability or reusability of components. Three different fabrication technologies for disposable THz resonator chips are investigated.

There is a great need for a low cost and sensitive method to measure infrared spectra of solid organic compounds in the gas phase. To record such spectra, we propose an optical parametric generator-based photoacoustic spectrometer, which emits in the mid-infrared fingerprint region between 3 and 4 microns. In this system, the sample is heated in a vessel before entering a home built photoacoustic cell, where the gaseous molecules are excited by a tunable laser source with a frequency repetition rate that matches the first longitudinal resonance frequency of the photocaoustic cell. In a first phase, we have focused on low-melting point stimulants such as Nikethamide, Mephentermine sulfate, Methylephedrine, Ephedrine and Pseudoephedrine. The vapor-phase spectra of these doping substances were measured between 2800 and 3100 cm-1, where fundamental C-H stretching vibrations take place. Our spectra show notable differences with commercially available condensed phase spectra. Our scheme enables to measure very low vapor pressures of low-melting point (<160 °C) solid organic compounds. Furthermore, the optical resolution of 8 cm-1 is good enough to distinguish closely related chemical structures such as the Ephedra alkaloids Ephedrine and Methylephedrine, but doesn't allow to differentiate diastereoisomeric pairs such as Ephedrine and Pseudoephedrine, two important neurotransmitters which reveal different biological activities. Therefore, higher resolution and a system capable of measuring organic compounds with higher melting points are required.

The sensor is dedicated to the detection of allergens. We use a biochemical reaction in the vicinity of the core of an optical fiber which modifies the propagation conditions of the optical wave by evanescent coupling. The detection involves a intrinsic optical fiber Fabry-Perot interferometer.

SINPHOS is a monolithic micro-device, able to measure simultaneously time distribution and spectrum of photons coming from a weak source like Delayed Luminescence of biological systems. In order to achieve this challenging goal, we use: Deep Lithography with Ions (DLI) and microelectronic technologies for the fabrication of dedicated passive micro-optical elements and for the realization of Single Photon Avalanche Diode (SPAD) detectors, respectively

We demonstrate the use of a series of in-line fibre long period grating curvature sensors on a garment, used to monitor the thoracic and abdominal volumetric tidal movements of a human subject. These results are used to obtain volumetric tidal changes of the human torso showing reasonable agreement with a spirometer used simultaneously to record the volume at the mouth during breathing. The curvature sensors are based upon long period gratings written in a progressive three layered fibre that are insensitive to refractive index changes. The sensor platform consists of the long period grating laid upon a carbon fibre ribbon, which is encapsulated in a low temperature curing silicone rubber.

A novel multi-channel detection system for real-time PCR machine is proposed in this study. The prototype in this article is equipped with a spectrometer which has the bandwidth of visible light, hence there are more than 6 channels can be detected simultaneously. In contrast to the traditional Real-Time PCR machine with discrete fluorescence wavelength detection channels, the prototype is equipped with continuous fluorescence wavelength detecting ability to multiplex Real-Time PCR. In this study, a HBV DNA template with LC-Red 640 dye and the Internal Control DNA template with LC-Red 705 dye were employed for DNA quantification experiments. The results show that this prototype provides comparable accuracy and reproducibility as the commercial system for DNA quantification with the DNA quantification and detection method proposed in this study.

A primary goal of preventive oncology is the identification of women at increased risk for breast cancer who would benefit most from risk reducing interventions. An established physical risk assessment technique is the use of mammography to quantify the dense tissue content of the breast. Women with a majority of the breast occupied by dense tissue are at four to six times greater risk of breast cancer than women with the least density. The main drawback of mammography is that it requires exposure to ionising radiation and there are concerns regarding use in young women. Another potential physical risk assessment is Transillumination Breast Spectroscopy (TIBS). TIBS uses non-ionizing optical radiation to measure bulk tissue properties and thus is applicable to women of any age. This study examines the feasibility of using TIBS in vivo to detect mammographic density as an interim indicator of breast cancer risk. TIBS measurements were completed on 300 women with radiological normal mammograms. White light (625 to 1060 nm) was delivered to the breast tissue and transmitted light was detected on the opposite side of the breast. Principal component analysis was used to reduce the spectral data and generate individual 'risk' scores. Agreement between the obtained 'risk' scores and mammographic density was established using density cluster analysis, the Kappa statistic and logistic regression. The agreement between breast density assessed by mammography and by TIBS was statistically significant for all 'risk' scores. Logistic regression indicated a strong association between the TIBS scores and mammographic density. TIBS provides an alternative to x-ray derived mammographic density as a biomarker of breast density and hence cancer risk.

Reactive hyperemia signals obtained with laser Doppler flowmetry are currently used to diagnose peripheral arterial occlusive diseases (PAOD). De-noising of such signals could lead to improved diagnoses. For this purpose, the principal components analysis is applied to signals acquired on PAOD and healthy subjects.

Noninvasive method for blood glucose monitoring in cutaneous tissue based on reflective spectrometry combined with a thermal emission spectroscopy has been developed. Regression analysis, neural network algorithms and cluster analysis are used for data processing.