A Goniophotometer is a device used for measurement of the light emitted from an object at different angles. The use of goniophotometers has been increasing in recent years with the introduction of

LED A light-emitting diode (LED) is a semiconductor Electronics, device that Light#Light sources, emits light when Electric current, current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy i ...

-light sources, which are mostly directed light sources, where the spatial distribution of light is not homogeneous. If a light source is homogeneous in its distribution of light, it is called a Lambertian source. Due to strict regulations, the spatial distribution of light is of high importance to

automotive lighting The lighting system of a motor vehicle consists of lighting and signalling devices mounted to or integrated into the front, rear, sides, and in some cases the top of a motor vehicle. They illuminate the road ahead for the driver and increase t ...

and its design.

Uses

A goniophotometer can be used for various applications: * Measurement of

luminous flux In photometry, luminous flux or luminous power is the measure of the perceived power of light. It differs from radiant flux, the measure of the total power of electromagnetic radiation (including infrared, ultraviolet, and visible light), in th ...

of a light source * Measurement of

luminous intensity In photometry, luminous intensity is a measure of the wavelength-weighted power emitted by a light source in a particular direction per unit solid angle, based on the luminosity function, a standardized model of the sensitivity of the human eye. ...

distribution from a source much smaller than the size of the goniophotometer Equipped with color sensors additional characteristics can be measured * Distribution of

correlated color temperature Color temperature is the color of light emitted by an idealized opaque, non-reflective body at a particular temperature measured in kelvins. The color temperature scale is used to categorize the color of light emitted by other light sources ...

* Color uniformity

Types

The various types of goniophotometer are defined here which is derive from publication "CIE 70" from the

International Commission on Illumination The International Commission on Illumination (usually abbreviated CIE for its French name, Commission internationale de l'éclairage) is the international authority on light, illumination, colour, and colour spaces. It was established in 1913 a ...

Type A

Fixed horizontal axis, with the vertical axis attached, both perpendicular to the main output direction of the light source

Type B

Fixed vertical axis, with the horizontal axis attached, both perpendicular to the main output direction of the light source Type A and B are Double columns structure. This type is applied to fixed the grille lamp. The symmetry axis of lamp and the horizontal of rotating supporter is coaxial, in the B-βcoordinate system, and the two is vertical Cross, in the A-αcoordinate system.

Type C

Fixed vertical axis perpendicular to the line of measurement, with a horizontal axis parallel to the main output direction of the light source Type C are single column structures. The single column structure is created when the assistant column is taken down from double columns structure. This type is applied to a fixed tube lamp, spot lamp, or other devices. The axis radiation of lamp and the horizontal of rotating supporter is coaxial.

References