Stéphane Bourquin

HEPIA - University of Applied Sciences and Arts Western Switzerland

During the process of parts produced by texturing laser machine, the dimensional verifications are done manually. For a specified kind of laser, the machining pass may remove approximately few hundred nanometers of material to a maximum depth of 150µm after several sequences. If one could perform at least one measure after each laser pass, the mach...

Background Lung auscultation is fundamental to the clinical diagnosis of respiratory disease. However, auscultation is a subjective practice and interpretations vary widely between users. The digitization of auscultation acquisition and interpretation is a particularly promising strategy for diagnosing and monitoring infectious diseases such as Cor...

A compact binocular heads-up display integrated in a motorcycle helmet is presented and characterized. The use of a laser micro-projector using a 2D MEMS-mirror enables the formation of a bright image, superimposed on the user vision. A fully-functional and adjustable 3D-printed prototype, thereby fitting the morphology of most users, is presented.

We present a compact binocular head-up display for integration in a motorcycle helmet. A 2D MEMS-mirror reflecting laser beams enables the formation of a bright image superimposed on the user vision by means of retinal scanning. A 3d-printed prototype including the required optical components is presented and characterized. It fits the morphology o...

The objective of this study was to develop and verify a new technique for monitoring the progression of osteoarthritis (OA) by combining a rat model with the imaging modality optical coherence tomography (OCT). Time-sequential, in vivo, OCT imaging was performed on the left femoral condyles of 12 Wistar rats following sodium-iodoacetic acid-induced...

Ultrahigh-resolution optical coherence tomography (OCT) has an axial resolution of <5 microm, 2 to 3 times finer than standard OCT. This study investigates ultrahigh-resolution and three-dimensional OCT for ex vivo imaging of the large and small intestines and correlates images with histology. Ultrahigh-resolution OCT imaging was performed on fresh...

We present a new model of optical coherence tomography (OCT) taking into account multiple scattering. A theoretical analysis and experimental investigation reveals that in OCT, despite multiple scattering, the field backscattered from the sample is generally spatially coherent and that the resulting interference signal with the reference field is s...

We present a comprehensive study of multiple-scattering effects in wide-field optical coherence tomography (OCT) realized with spatially coherent illumination. Imaging a sample made of a cleaved mirror embedded in an aqueous suspension of microspheres revealed that, despite temporal coherence gating, multiple scattering can induce significant coher...

We present a semi-analytical model of optical coherence tomography (OCT) taking into account multiple scattering. The model rests on the assumptions that the measured portion of the backscattered sample field is spatially coherent and that the sample is motionless relative to measurement time. This allows modeling an OCT signal as a sum of spatiall...

We present a semi-analytical model of optical coherence tomography (OCT) taking into account multiple scattering. The model rests on the assumptions that the measured portion of the backscattered sample field is spatially coherent and that the sample is motionless relative to measurement time. This allows modeling an OCT signal as a sum of spatiall...

We present a new light source for parallel Optical Coherence Tomography (OCT) based on multiple waveguides written in Ti:sapphire. Each channel can generate a spectrum of 174 nm bandwidth centered at 772 nm, with an optical power on sample of 30 mu W. A system depth resolution of 1.9 mu m is obtained, which correspond to 1.5 mu m in tissue.

We present a new light source for parallel OCT based on multiple waveguides written in Ti:sapphire. Each channel can generate a spectrum of 174 nm bandwidth centered at 772 nm, with an optical power on sample of 30 µW. A system depth resolution of 1.9 µm is obtained, which correspond to 1.5 µm in tissue.

Optical coherence tomography (OCT) is a recent technique for biomedical imaging. Tomographic images with micrometer resolution can be generated using fiber interferometers with broadband light sources. The longitudinal resolution of such instruments is inversely proportional to the optical bandwidth of the light source. Femtosecond Ti:sapphire lase...

Current spectroscopic optical coherence tomography (OCT) methods rely on a posteriori numerical calculation. We present an experimental alternative for accessing spectroscopic information in OCT without post-processing based on wavelength de-multiplexing and parallel detection using a diffraction grating and a smart pixel detector array. Both a con...

Ultrahigh resolution, real time OCT imaging is demonstrated using a compact femtosecond Nd:Glass laser that is spectrally broadened in a high numerical aperture single mode fiber. A reflective grating phase delay scanner enables broad bandwidth, high-speed group delay scanning. We demonstrate in vivo, ultrahigh resolution, real time OCT imaging at...

A new femtosecond pump–probe spectroscopy technique is demonstrated that permits the high-speed, parallel acquisition of pump–probe measurements at multiple wavelengths. This is made possible by use of a novel, two-dimensional smart pixel detector array that performs amplitude demodulation in real time on each pixel. This detector array can not onl...

Ultrahigh resolution OCT is used to visualize experimentally induced osteoarthritis in a rat knee model. Using a Cr4+:Forsterite laser, ultrahigh image resolutions of 5um are achieved. Progression of osteoarthritic remodeling and cartilage degeneration are quantified. The utility of OCT for the assessment of cartilage integrity is demonstrated.

We demonstrate compact ultrahigh resolution OCT systems for in vivo studies, with broadband light sources based on a commercially available Nd:Glass femtosecond laser and nonlinear fiber continuum generation. In vivo OCT images of hamster cheek pouch and human skin acquired at 4 frames per second and with 5.5 mum axial resolution are presented. The...

A report is presented on laser advances which benefit optical coherence tomography. Optical coherence tomography is an emerging technology that generates high-resolution, cross-sectional images of internal microstructures in biological tissues, in situ and in real time. It is reported that the new developments promise to improve resolution, enablin...

We demonstrate and compare alternate scanning methods in optical coherence tomography for achieving high resolution imaging. These techniques enable high transverse resolutions and overcome depth of field limitations. Cellular level resolutions in human tissue may be achieved.

We demonstrate real time, ultrahigh resolution OCT imaging using a portable mode-locked Cr:forsterite laser. OCT imaging at 5.5 um axial resolution was performed of normal and cancerous human prostate tissue and correlated with histology.

Ultrahigh resolution OCT imaging is demonstrated using compact broadband light sources based on a commercially available Nd:Glass femtosecond laser with nonlinear fiber continuum generation. A tapered single mode fiber is used to generate broadband light centered at 1300 nm. Broadband light near 1064 nm can also be generated using a high numerical...

Real-time optically sectioned microscopy is demonstrated using an AC-sensitive detection concept realized with smart CMOS image sensor and structured light illumination by a continuously moving periodic pattern. We describe two different detection systems based on CMOS image sensors for the detection and on-chip processing of the sectioned images i...

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We demonstrate methods for achieving high resolution imaging using alternate scanning techniques in optical coherence tomography and optical coherence microscopy. These techniques enable high transverse resolutions and overcome depth of field limitations. Cellular level resolutions in human tissue may be achieved.

A new method for simultaneously acquiring pump-probe signals at several wavelengths using a smart pixel detector array and broadband femtosecond laser has been demonstrated and promises to be a powerful technology for performing rapid, high sensitivity, wavelength-dependent pump-probe spectroscopy

Parallel optical coherence tomography in scattering samples is demonstrated using a 58 x 58 smart-pixel detector array. A femtosecond mode-locked Ti:Sapphire laser in combination with a free space Michelson interferometer was employed to achieve 4 mum longitudinal resolution and 9 mum transverse resolution on a 260 x 260 mum field of view. We image...

Femtosecond pump-probe spectroscopy is a well-known method used to investigate ultrafast excited state dynamics in condensed matter, chemical, and biological systems. The standard technique uses a narrowband pump and continuum probe to excite the sample, and employs a spectrometer to acquire the wavelength dependent absorption saturation dynamics....

Parallel optical coherence tomography in scattering samples is demonstrated using a 58 by 58 smart-pixel detector array. A femtosecond mode-locked Ti:Sapphire laser in combination with a free space Michelson interferometer was employed to achieve 4micrometers longitudinal resolution and 9mm transverse resolution on a 260x260 micrometers 2 field of...

A 58×58 pixel CMOS detector array for on-chip amplitude demodulation on all pixels in parallel is presented. Optical signals can be detected at Doppler frequencies of 1 kHz up to 1 MHz, with a dynamic range of 57 dB, and at a pixel readout rate of up to 3 MHz

A low-coherence reflectometer based on a conventional Michelson interferometer and a novel silicon detector chip with a two-dimensional array of pixels that allows parallel heterodyne detection is presented. We demonstrate acquisition of three-dimensional images with more than 100,000 voxels per scan at a sensitivity of - 58 dB and a rate of 6 Hz.

Parallel optical coherence tomography in scattering samples is demonstrated using a 58 by 58 smart-pixel detector array. A femtosecond mode-locked Ti:Sapphire laser in combination with a free space Michelson interferometer was employed to achieve 4μm longitudinal resolution and 9μm transverse resolution on a 260×260 μm ² field of view. We imaged a...

A low-coherence reflectometer based on a conventional Michelson interferometer and a novel silicon detector chip that allows parallel heterodyne detection is presented. Cross-sectional images of 64 × 256 pixels covering an area of 1.92 mm × 1.3 mm are acquired at video rate and with a sensitivity close to the shot-noise limit. Applications in surfa...

Many biological tissues and a lot of technical objects of interest are to a certain degree transparent to light in the visible and near infrared wavelength range of the electromagnetic spectrum. Nevertheless, it has not been possible for a long time to create clear optical images of these objects due to the multiple scattering of a large part of th...