Device for analyzing a polyphase mixture via a light beam backscattered by said mixture, comprising: - said polyphase mixture; - a cell having a capacity component of vertical extent, capable of containing the polyphase mixture, - means for emitting a light beam in the direction of the cell, so that the light beam extends in a vertical plane covering at least a height (hc) of the cell containing the polyphase mixture, - means for receiving at least a part of the light beam backscattered by said polyphase mixture, covering a backscattered light beam height extending over the height (hc) of the cell containing the polyphase mixture, - optical conjugation means arranged between the cell and the means for receiving at least a part of the light beam backscattered by the polyphase mixture, - said means for receiving comprising a matrix sensor provided with a plurality of pixels, forming a surface for receiving said at least part of the backscattered light beam, extending along a vertical direction and a horizontal direction, - means for analyzing said at least part of the light beam backscattered by the polyphase mixture and received by the matrix sensor via the optical conjugation means, - the light beam emitted in the direction of the cell having, at its interface between the inner surface of the wall of the cell and the polyphase mixture, a vertical line shape whose width is less, preferably very much less, than the free transport path (l*) of the polyphase mixture, - the means for analyzing comprising the selection of pixels of an horizontal line of the matrix sensor corresponding to a given height (h1, h2), said selection resulting in obtaining a transverse profile of light intensity of said pixels, and the calculation of the integral of the transverse profile of light intensity, representative of the diffusing properties of the polyphase mixture at the given height (h1, h2). - said polyphase mixture; - a cell having a capacity component of vertical extent, capable of containing the polyphase mixture, - means for emitting a light beam in the direction of the cell, so that the light beam extends in a vertical plane covering at least a height (hc) of the cell containing the polyphase mixture, - means for receiving at least a part of the light beam backscattered by said polyphase mixture, covering a backscattered light beam height extending over the height (hc) of the cell containing the polyphase mixture, - optical conjugation means arranged between the cell and the means for receiving at least a part of the light beam backscattered by the polyphase mixture, - said means for receiving comprising a matrix sensor provided with a plurality of pixels, forming a surface for receiving said at least part of the backscattered light beam, extending along a vertical direction and a horizontal direction, - means for analyzing said at least part of the light beam backscattered by the polyphase mixture and received by the matrix sensor via the optical conjugation means, - the light beam emitted in the direction of the cell having, at its interface between the inner surface of the wall of the cell and the polyphase mixture, a vertical line shape whose width is less, preferably very much less, than the free transport path (l*) of the polyphase mixture, - the means for analyzing comprising the selection of pixels of an horizontal line of the matrix sensor corresponding to a given height (h1, h2), said selection resulting in obtaining a transverse profile of light intensity of said pixels, and the calculation of the integral of the transverse profile of light intensity, representative of the diffusing properties of the polyphase mixture at the given height (h1, h2).