Chromatic Dispersion Based Wide-Band, Fiber-Coupled, Tunable Light Source for Hyperspectral Imaging

Hyperspectral imaging is a powerful label-free imaging technique that provides topological and spectral information at once. In this work, we have designed and characterized a hyperspectral source based on the chromatic dispersion property of off-the-shelf lenses and converted a supercontinuum laser light source into a hyperspectral imaging light source for 490 nm to 900 nm wavelength range with a spectral resolution of 3.5 nm to 18 nm respectively. The potential of the source was demonstrated by imaging two color dots with different absorption bands. Further, we generated the hypercube of the lily ovary and dense connective tissue and measured their spectral signature as a function of wavelength. We also imaged the lower tongue of a healthy volunteer at 540 nm, 630 nm, and white light. Our simple hyperspectral light source design can easily be incorporated in a standard endoscope or microscope to perform hyperspectral imaging

Rapid high-resolution mid-IR imaging for molecular spectral histopathological diagnosis of oesophageal cancers

This thesis is written as part of Marie-Curie international training network called Mid-TECH. Mid-TECH is devoted to improve mid-infrared (MIR) technologies and consists of 15 PhD projects across European universities. This thesis aims to evaluate new technologies and concepts developed by the project partners for their applicability in a biomedical setting. The clinical problem to diagnose oesophageal cancers serves as an example case for this. The thesis consists of three projects all aimed to further the understanding of MIR hyperspectral imaging. The first project discussed in chapter 5 demonstrates the use of an new design of the United States Airforce resolution test chart. The new test chart is developed to evaluate spatial resolution of MIR hyperspectral imaging systems. The use of different materials is discussed and the new iteration of the thes chart is evaluated using a state of the art MIR imaging system. The second project discussed in chapter 6 evaluates the technical differences and their practical implications of discrete frequency MIR imaging systems compared to continuum source systems. A comparison of the two system types is drawn for imaging paraffin embedded sections of oesophageal tissue. Furthermore the effect of chemically removing the paraffin from the sample is compared to a mathematical correction algorithm. The system performance is compared based on their ability to differentiate healthy from cancerous tissue. The third project discussed in chapter 7 evaluates the potential of a new MIR detection scheme called upconversion in combination with a novel MIR laser source. It is a prove of concept study demonstrating that those two technologies can be deployed to do hyperspectral imaging in the MIR.European Commissio

Applications of spatial light modulators in Raman spectroscopy

Advances in consumer display screen technologies have historically been adapted by researchers across the fields of optics as they can be used as electronically controlled spatial light modulators (SLMs) for a variety of uses. The performance characteristics of such SLM devices based on liquid crystal (LC) and digital-micro-mirror device (DMD) technologies in particular has developed to the point where they are compatible with increasingly sensitive instrumental applications, for example Raman spectroscopy. SLMs provide additional flexibility, from modulation of the laser excitation (including multiple laser foci patterns), manipulation of microscopic samples (optical trapping) or selection of sampling volume (adaptive optics or spatially offset Raman spectroscopy), to modulation in the spectral domain for high-resolution spectral filtering or multiplexed/compressive fast detection. Here, we introduce the benefits of different SLM devices as a part of Raman instrumentation, and provide a variety of recent example applications which have benefited from their incorporation into a Raman system

Non-Invasive Assessment of Dairy Products Using Spatially Resolved Diffuse Reflectance Spectroscopy

The quality of a dairy product is largely determined by its microstructure which also affects its optical properties. Consequently, an assessment of the optical properties during production may be part of a feedback system for ensuring the quality of the production process. This paper presents a novel camera-based measurement technique that enables robust quantification of a wide range of reduced scattering coefficients and absorption coefficients. Measurements are based on hyperspectral images of diffuse reflectance in the wavelength range of 470 to 1020 nm. The optical properties of commercially available milk and yogurt products with three different levels of fat content are measured. These constitute a relevant range of products at a dairy plant. The measured reduced scattering properties of the samples are presented and show a clear discrimination between levels of fat contents as well as fermentation. The presented measurement technique and method of analysis is thus suitable for a rapid, non-contact, and non-invasive inspection that can deduce physically interpretable properties. </jats:p