Goniophotometrar

Goniophotometrar are instruments used to measure the angular distribution of light emitted by a light source or luminaire. They provide data about how intensity varies with direction, enabling the creation of photometric distributions essential for lighting design and product testing.

In typical operation, a detector observes the emitted light as the source or detector moves to sample different polar (theta) and azimuth (phi) angles. The measured quantity is the luminous intensity I(θ, φ) in candela per steradian, from which total flux, efficacy, and directional performance can be derived. Modern systems may use single detectors on a rotating arm, dual-axis scanners, or imaging cameras to capture 3D distributions.

Goniophotometers come in several configurations: traditional rotary devices around a fixed sample; hemispherical measurement instruments; imaging goniophotometers that capture a full 360×180 degree map; and portable or bench-top variants. They can be monochromatic or broadband, depending on detectors and filters, and may be integrated with integrating spheres for certain measurements.

Common applications include characterizing LEDs, lamps, and luminaires for compliance with lighting standards, design optimization, and photometric file generation (such as IES or EULUMDAT formats). The resulting data support lighting simulations and evaluation of glare, brightness uniformity, and directional performance.