It is disclosed a device for measuring a concentration of glucose, for example, in a translucent piece of a body, like an earlobe, a tissue connecting two fingers, a nasal ala, or a cheek. The piece is illuminated by a linearly polarized laser beam at a certain polarization direction. Consequently, a diffused radiated light is emitted from the piece, including a directed beam. The device includes a polarizing beam splitter which receives the directed beam, a lens, a sensor array, and means for connecting to a processor. The splitter splits components of the directed beam at two mutually orthogonal linear polarization directions into two polarized beams propagating at two respective different directions. The lens images the distribution of the directed beam on the translucent piece on two spatially separated groups within the sensor arrays. The processor defines pixel pairs from a first and second images which correspond to a same point on the second surface of the translucent piece, and subtracts the first pixels from the respective second pixels to get a difference image. In addition, the processor calculates the variance of the difference image, and calculates the desired concentration accordingly.
