A laser scanner (100, 122, 162, 166, 180) to detect objects in a scanning area, the laser scanner comprising: a light source which in operation emits a light beam; a scanning mirror rotatable about a vertical axis of rotation which reflects the light beam from the light source toward the scanning area and which reflects return light from objects in the scanning area; a collecting mirror dimensioned and positioned to receive the return light from the scanning mirror; an interference filter disposed between the collecting mirror and the scanning mirror, in operation the interference filter filters the return light from the scanning mirror and provides the filtered return light to the collecting mirror; a light detector; a protective window disposed between the scanning mirror and the scanning area which is transmissive to the light beam, at least a portion of the protective window being rotationally symmetrical about the axis of rotation of the scanning mirror and having an inward facing surface tilted with respect to the axis of rotation; whereby the light detector is disposed between the interference filter and the collecting mirror and, in operation, receives the filtered return light reflected from the collecting mirror, and in that the laser scanner comprises: a light absorptive plate (144, 168) disposed horizontally inward of the protective window, vertically below said at least a portion of the protective window and vertically between the scanning mirror and the collecting mirror, the light absorptive plate (144, 168) receiving a reflective component of the light beam from the inward facing surface of the protective window and comprising a central opening which provides an optical path between the scanning mirror and the collecting mirror. a light source which in operation emits a light beam; a scanning mirror rotatable about a vertical axis of rotation which reflects the light beam from the light source toward the scanning area and which reflects return light from objects in the scanning area; a collecting mirror dimensioned and positioned to receive the return light from the scanning mirror; an interference filter disposed between the collecting mirror and the scanning mirror, in operation the interference filter filters the return light from the scanning mirror and provides the filtered return light to the collecting mirror; a light detector; a protective window disposed between the scanning mirror and the scanning area which is transmissive to the light beam, at least a portion of the protective window being rotationally symmetrical about the axis of rotation of the scanning mirror and having an inward facing surface tilted with respect to the axis of rotation; whereby the light detector is disposed between the interference filter and the collecting mirror and, in operation, receives the filtered return light reflected from the collecting mirror, and in that the laser scanner comprises: a light absorptive plate (144, 168) disposed horizontally inward of the protective window, vertically below said at least a portion of the protective window and vertically between the scanning mirror and the collecting mirror, the light absorptive plate (144, 168) receiving a reflective component of the light beam from the inward facing surface of the protective window and comprising a central opening which provides an optical path between the scanning mirror and the collecting mirror.