Source: Neumüller Elektronik

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The Concept of Luminous Flux

In the field of radiometry, luminous flux is a photometric quantity that measures the total amount of visible light emitted by a light source per unit time. Unlike radiant flux, which quantifies all emitted optical energy, luminous flux takes into account the sensitivity of the human eye. It is expressed in lumens (lm) and considers the photopic response of the human eye under normal lighting conditions.

Significance of Luminous Flux

Luminous flux is a crucial specification for light sources used in illumination applications, such as incandescent lamps, fluorescent lamps, and LEDs. It indicates how much a light source contributes to the overall illumination of a space. For example, a 60-W incandescent lamp may produce 900 lumens of luminous flux, with a luminous efficacy of 15 lm/W. In comparison, an LED lamp can achieve the same luminous flux with significantly lower power consumption due to its higher luminous efficacy.

Relation to Luminous Intensity and Illuminance

Luminous flux does not provide information on the directionality of light emission. Luminous intensity, measured in candela, represents the luminous flux per unit solid angle. For light sources with directional emission, like lasers, higher illuminance levels can be achieved with the same luminous flux. Illuminance, measured in lux, quantifies the luminous flux incident on a surface area.

Measurement of Luminous Flux

The measurement of luminous flux depends on the light source’s emission characteristics. For directional sources like lasers, a simple optical power meter suffices. However, for sources emitting light in various directions, such as LEDs, an integrating sphere is used to capture and measure the total luminous flux. This method ensures an accurate assessment of the light source’s illuminating capabilities.

Conclusion

Understanding luminous flux is essential in evaluating the lighting performance of different light sources. By considering luminous flux, luminous intensity, and illuminance, one can make informed decisions when selecting lighting solutions for various applications.

Source: Zumtobel.us
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