Abstract: 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.

Abstract: A luminaire (1) comprises a reflector (3) that defines an elongate concave cavity in which an elongate light source (2), for example a fluorescent tube, is located in spaced relationship to the reflector whereby the latter surrounds the light source on its rearward side to reflect light from the source and cause it to be emitted from the cavity in a generally-forwards direction. To enable the distribution of light from the luminaire (1) to be tailored to meet the requirements of the situation in which the luminaire is to be used, the reflector (3) is provided, on opposite sides of the cavity, with a respective prismatic structure (6) upstanding from its inner surface to intercept and deviate light that is emitted, in the generally-forwards direction, from the space in the cavity between the light source (2) and the reflector (3).

Abstract: 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.

Abstract: A modulation assembly includes a fibre having a drawn tapered portion, and apparatus for applying a perturbation to the tapered portion to vary the percentage transmission through the fibre.