Terminology

  • Efficiency (Optical)

    At Carclo Optics the optical effciency is determined as the total luminous flux collected by a hemisphere placed over the optical assembly divided by the total lumen output of the LED source(s). It is expressed as a percentage. 

  • Far Field

    This is a notional measure of the distance from a light source.  It occurs when the observation plane is much further from the source than 10x the largest transverse dimension within the source. In this regime, sources can be approximated as point sources.

  • Field-Angle

    A measure of the width of a distribution defined as the separation of the data points on either side of the peak which have values equal to 10% of the maximum. For intensity distributions this is the angular range at which the intensity falls to 1/10th  of its maximum value.

  • Foot-Candle

    A measure of illumination used to describe how much light is falling within a given area. 1 Foot-Candle = one lumen per square foot

  • Freeform Optic

    these allow a designer to replace the outputs from a mixture of different optic types and merge these into one single-optic to give unique, non-symmetrical illumination patterns, for example Streetlighting.

  • Fresnel Lens

    A thin optical lens consisting of concentric rings of segmental lenses and having a short focal length. These are typically designed for visible or near infra-red wavelengths.

  • FWHM (Full Width Half Maximum)

    A measure of the width of a distribution defined as the separation of the data points on either side of the peak which have values equal to 50% of the maximum. For intensity distributions this is the angular range at which the intensity falls to half its maximum value.

  • IES

    The IES file is a photometric file typically used to describe the light distribution from any optic, lighting fixture or source. Certain optical simulation packages (e.g. Dialux, Relux, etc.) use IES files to predict expected optical performance. The IES file re-creates the light intensity distribution, so it only contains angular information. It also assumes the light source is a point (i.e. it has no size) and the surface or object you wish to illuminate are in the ‘Far-field’. If you want to model the performance of an additional optic with our Carclo optic then you need the ‘Ray set’ for that particular optic. The Rayset contains positional & angular data (i.e. Near-field data).

  • IGES or IGS

    This is one type of file format (e.g. 'Part name.IGES') used to save and exchange CAD data. Not to be confused with IES files – see above. Note, that any IGES files on our website are simplified representations of the true optical geometry and are not suitable for optical ray-tracing.

  • Illuminance

    Illuminance is, in simple terms, a measure of the amount of light (in lumens) emitted from a light source onto a surface at a specific distance. The SI unit for Illuminance is Lux (i.e. lumens per m2). In the far-field, as the distance from a light source increases the Lux level drops in proportion to the distance squared – the Inverse square law.

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