Goniophotometer
A goniophotometer is a photometer for measuring the directional light distribution characteristics of light sources, luminaires, optical media, and surfaces. A goniophotometer typically incorporates a goniometer that measures direction using spherical coordinates to capture the angular distribution of the transmitted, emitted, or reflected light. A gonioradiometer differs only in that it is a radiometer (i.e., is not specific to human vision), rather than a photometer.
A goniophotometer enables characterization of emitted light that is not isotropic. The directional distribution of light is of high importance to architectural lighting, automotive lighting, and other applications. It is typically referred to as the luminous intensity distribution when expressed in terms of angular coordinates. It is sometimes referred to as the beam pattern, but this term can also refer to the pattern of light displayed on a surface normal to the beam axis.