Christian Depeursinge

Clinical imaging fluorescence apparatus for the endoscopic photodetection of early cancers by use of Photofrin II

A fluorescence imaging device applied to the detection of early cancer is described. The apparatus is based on the imaging of laser-induced fluorescence of a dye that localizes in a tumor with a higher concentration than in the surrounding normal tissue after iv injection. Tests carried out in the upper aerodigestive tract, the tracheobronchial tree, and the esophagus with Photofrin II (1 mg/kg of body weight) as the fluorescent agent are reported as examples. The fluorescence is induced by violet (410-nm) light from a continuous-wave (cw) krypton-ion laser. The fluorescence contrast between tumor and surrounding tissue is enhanced by real-time image processing. This is done by the simultaneous recording of the fluorescence image in two spectral domains (470-600 and 600-720 nm), after which these two images are digitized and manipulated with a mathematical operator (look-up table) at video frequency. Among the 7 photodetections performed in the tracheobronchial tree, 6 were successful, whereas it was the case for only 5 of the 15 lesions investigated in squamous mucosa (upper aerodigestive tract and esophagus). The sources of false positives and false negatives are evaluated in terms of the fluorescent dye, tissue optical properties, and illumination optics.

Extended Depth-of-Field and 3D Information Extraction in Digital Holographic Microscopy

A comparison of algorithms for depth-of-field extension in the particular field of digital holographic microscopy is presented. Using the reconstruction properties of holography, a simple 3D reconstruction method from a single hologram is deducted.

Small reconstruction distance in convolution formalism

Different numerical wavefront propagations in Fresnel approximation are proposed in digital holography. Standard convolution formalism fails for small reconstruction distances. We developed a simplified convolution formalism that is equivalent to the angular spectrum.

Microlenses metrology with digital holographic microscopy

Digital holographic Microscopy (DHM) is an imaging modality reconstructing the wavefront in a numerical form, directly from a single digitalized hologram. It brings quantitative data derived simultaneously from the amplitude and phase of the complex reconstructed wavefront diffracted by the object and it is used to determine the refractive index and/or shape of the object with accuracy in the nanometer range along the optical axis. DHM comprises a microscope objective to adapt the sampling capacity of the camera to the information content of the hologram. This paper illustrates some of the possibilities offered by DHM for micro-optics quality control. Actual results obtained by DHM, yielding an axial precision up to 3.7 nm, will be compared with measurements performed with interferometers by SUSS MicroOptics SA and with the profiles measured with a mechanical scanning probe instrument (Alpha step 200 from Tencor Instrument). Two different micro-lenses arrays where tested: a quartz refractive lenses array (observed with transmission DHM) and a Silicon refractive lens array (observed with reflection DHM).

Real-time dual-wavelength digital holographic microscopy for MEMS characterization

We present a method to achieve real-time dual-wavelength digital holographic microscopy (DHM) measurements of micro-electro-mechanical systems (MEMS) with a single camera acquisition. Indeed, while DHM is a technique of choice for MEMS investigation, thanks to its high-speed full-field complex wavefront reconstruction compatible with stroboscopic or pulsed operation modes, the nanometer-resolved phase information available suffers from a so-called phase ambiguity when the optical path length (OPL) induced by the sample is larger than the laser wavelength (typically 400-700nm in the visible range). This measurement range limitation is due to the periodic nature of the phase and, although unwrapping algorithms may be used in some cases, it represents an obstacle to widen DHM applications range. Here we introduce a technique for two-wavelengths DHM, extending the technology field of applications to the micro-meter range, and this with a single hologram acquisition to stay compatible with the exclusive DHM high-speed capabilities described above. Examples of investigation on a 1Hz moving micro-mirror at video frequency are shown to demonstrate the interest of the method for MEMS monitoring.

Real-Time Birefringence Measurement with Digital Holographic Microscopy

Digital holographic microscopes using two orthogonal polarized reference waves provides real-time polariscopes. Birefringence induced by internal stress is imaged in optical fibers and in fused silica substrates, where lines are written with low-energy femtosecond pulses.

Portable Off-axis Camera for Quantitative Phase Microscopy

A portable camera system based on holographic elements is demonstrated which can be attached to the camera port of a conventional microscope for complex wavefront analysis. The full-field off-axis holograms provide the whole sample information.

Measuring Shape and Surfaces down to the Nanometer and Nanosecond scales by Digital Holographic Microscopy

Keywords: [MVD] Reference LOA-CONF-2009-030 Record created on 2009-09-17, modified on 2017-05-10