Apparatus for determining information associated with reflection characteristics of a surface comprising a sensor (60) configured to generate sensor output dependent on an intensity of light incident on the sensor and having a field of view directed at an external surface (57) in use an illumination source (58) configured to emit light onto the external surface in use an optically transparent window (61) located such as to allow light to pass from the illumination source to the external surface and to allow light to pass to the sensor from the external surface in use a light concentrator (66) fixed to or integral with the window, the light concentrator being configured to concentrate at least some light from the illumination source onto the external surface in use such that the concentrated light may be reflected from the external surface onto the sensor via the window and a processor (40) configured to use the sensor output to determine information associated with reflection characteristics of the external surface.
