A light guide (1) comprises a housing (3) defining a light-guiding
optical cavity having first and second opposed major faces (5, 6), and a
light source (11) arranged to direct light into the cavity from one end,
to be guided between the major faces. The first major face (5) comprises
a window through which light can be emitted from the optical cavity to be used,
for example, for illuminating a graphic display. To improve the light distribution
across that first major face (5), the second major face (6) comprises
a sheet material (23) having a specularly-reflecting surface (24)
that faces into the optical cavity and has diffusely-reflecting light-extraction
elements (27) applied thereto in a predetermined configuration for causing
light to be emitted from the optical cavity through the said window.
