A goniophotometer measures the variation of luminous intensity (expressed in candelas) with angle from a light source. Goniophotometers are often used to generate so-called “photometric data files” for lighting products in either the standard IESNA (.ies) or EULUMDAT (.ldt) formats. Applications of goniophotometers include the testing of general or architectural lighting products, UVC germicidal lighting, vehicle lighting (headlamp and marker), flashing visual alert devices, road traffic signals, airfield and aircraft lighting.
Please note that not all light fittings require a true goniophotometric measurement. For any lamp that has a narrow beam angle (e.g. spot light, vehicle headlamp), there is a much simpler solution. By projecting the beam onto a matte white screen and recording the beam pattern with an imaging photometer, you can record goniometric intensity data instantaneously with no moving parts. For measuring the view angle of a display, an imaging photometer can be combined with a conoscopic lens.
SphereOptics supplies the photometric test equipment designed and manufactured by SSL Resource Ltd in Salo, Finland. A wide range of goniophotometers is offered that are optimised for different budgets and sample sizes and weights. Both IES type B and type C motion goniometer stages are available (click here for explanation of motion types), with the option of converting certain models between motion types. This inherent flexibility allows one goniophotometer to be used to test both general lighting products and (for example) vehicle lighting.