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Mise au point d’une chaîne de capture/ restitution stéréoscopique d’images couleurs : application à la conception d’interfaces adaptées aux déficients visuels

Abstract : This thesis is part of a project conducted by the LGI2P research center (IMT Mines Ales). The project's final aim is to help people with vision disorders suffering from retinitis pigmentosa and glaucoma get back to work and improve their daily lives. The final device is designed to help people in their mobility activities: detecting obstacles, searching for visual signals, by addressing problems related to dazzling and haemeralopia affecting these potential users.The research of this thesis has several contributions to the project. First of all, parameters characterizing the residual vision of each user had to be defined. Indeed, each patient has his own light comfort conditions, which depend in particular on his pathology's progress: at each stage of the evolution of their disease, patients have specific minimum luminosity limits below which they no longer perceive the details in a scene, and also on the maximum luminosity above which they feel discomfort and pain. The definition of these limitations in luminosity will make it possible to parameterize the device and adapt it to each user. But there is no method to measure these limiting luminance levels. We have therefore participated in the design and development of specialized tests, and in the conduct of trials on visually impaired subjects, as part of a clinical trial led by the Nîmes University Hospital and the ARAMAV (institute specializing in low vision functional rehabilitation), for medical research. We have also proposed a new test to measure sensitivity to chromatic contrast, always with the aim of better adjusting the images displayed to users' vision.Then, we developed a prototype of the device (cameras and virtual reality video headset). In order to achieve these results, we had to choose the image capture and display equipment. A colorimetric calibration work on these equipments allowed us to link digital quantities (RGB code) and physical quantities (luminance and chrominance). This stage is required to perform the above tests under physically known conditions. It also allowed us to define the physical characteristics of the equipment that would be selected to produce the final product, whether they are different from those required during our work.Finally, we discussed the processing to be applied to the signal captured by the camera. We have proposed real-time brightness treatments to increase brightness in dark areas of the image and decrease brightness in areas that dazzle the patient. We have presented the limitations of conventional imaging and the necessity to work on HDR (high dynamic range) images. We have compared several methods to allow the display of these HDR images on screens with lower dynamic range, looking for the image characteristics that these methods should better preserve, and taking into consideration the visual performance of potential users. We have also suggested color treatments by increasing contrast and saturation to make images more perceptible to patients with color vision disorders.
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Imad Benkhaled. Mise au point d’une chaîne de capture/ restitution stéréoscopique d’images couleurs : application à la conception d’interfaces adaptées aux déficients visuels. Autre [cs.OH]. Université Montpellier, 2018. Français. ⟨NNT : 2018MONTS037⟩. ⟨tel-02094447⟩

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