Abstract: A linear illumination unit (30) has a line of unlensed LEDs (31) which emit light spreading out. The light is focused into a line by a Fresnel lens (33) which allows spread and mixing of light in the linear direction and limits spread in the ortliogonal direction. A Fresnel lens is particularly effective for this purpose. The housings 34 have slots 36 to help control light spread, and the housings are open-ended to allow spread of light in the linear direction beyond the confines of the, geometry of the units. Thus, units (30) may be interconnected to provide seamless linear light in a modular manner.