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A non-invasive optical technique, based on a supercontinuum laser source and hyperspectral sensors, is established to measure the spectral degree of linear polarization (DOLP) in a broad spectral range from 525 nm to 1000 nm. Several biomaterials of interest, such as healthy and cancerous skins, are considered. The spectral DOLP of melanoma, from 5 mm to 9 mm diameter, are measured and analyzed. An increase of the spectral DOLP is reported for 100% of the melanoma samples compared to healthy skin samples. The spectral DOLP of a given melanoma appears to be correlated to the stage of its development: the larger the melanoma, the higher the DOLP. Such trend could be explained by a decrease of the surface roughness along the evolution of the disease. In addition, a significant spectral dependence of the DOLP is reported for melanoma samples as it exhibits a decrease in the near infrared from 750 nm to 1000 nm.

Since few years, a new type of camera is emerging on the market: a digital camera capable of capturing both the intensity of the light emanating from a scene and the direction of the light rays. This new camera technology called light-field camera uses an array of lenses placed in front of a single image sensor, or simply, an array of cameras attached together. In this paper, a new optical device is proposed: a 4 mini-lens ring which is inserted between the lens and the image sensor of a digital camera. This device prototype is able to convert a regular digital camera into a light-field camera as it makes it possible to record 4 sub-aperture images of the scene. It is a compact and cost-effective solution to perform both post-capture refocusing and depth estimation. The mini-lens ring makes also the plenoptic camera versatile; it is possible to adjust the parameters of the ring so as to reduce or increase the size of the projected image. Together with the proof of concept of this new device, we propose a method to estimate the positions of each optical component depending on the observed scene (object size and distance) and the optics parameters. Real-world results are presented to validate our device prototype.

We propose a model of depth camera based on a four-lens device. This device is used for validating alternate approaches for calibrating multiview cameras and also for computing disparity or depth images. The calibration method arises from previous works, where principles of variable homography were extended for three-dimensional (3-D) measurement. Here, calibration is performed between two contiguous views obtained on the same image sensor. This approach leads us to propose a new approach for simplifying calibration by using the properties of the variable homography. Here, the second part addresses new principles for obtaining disparity images without any matching. A fast algorithm using a contour propagation algorithm is proposed without requiring structured or random pattern projection. These principles are proposed in a framework of quality control by vision, for inspection in natural illumination. By preserving scene photometry, some other standard controls, as for example calipers, shape recognition, or barcode reading, can be done conjointly with 3-D measurements. Approaches presented here are evaluated. First, we show that rapid calibration is relevant for devices mounted with multiple lenses. Second, synthetic and real experimentations validate our method for computing depth images.

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