Lighting unit for producing linearly polarized light directed onto a target surface comprising a source unit producing light in the visible spectral range, and an optically translucent polarizing front unit (4) providing protection against external effects. The source unit and the polarizing front unit (4) are placed in a housing (8) in which an electric cable passes through. The source unit (1) contains at least one panel (2) having a number of high intensity LED devices (3) arranged in a predetermined pattern on one of its sides. The polarizing front unit (4) contains at least one optically transparent rigid carrier and a polarizing filter foil applied onto the carrier. The housing (8) keeps the polarizing front unit (4) in a fixed position so that they confine a hermetically closed inner space. The panel (2) is positioned parallel with the polarizing unit (4) within the inner space so that the LED devices (3) face towards the polarizing front unit (4).