Datasheet

31/07/2007 3/5 FCR-_1-XR79-0R reflector

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(2) To calculate the on-axis intensity, multiply the on-axis efficiency of the reflector (cd/lm) by the total flux of

the Cree LED used. See “Illumination Calculations” below. For more detail on flux binning please check

the Cree LED datasheet at

Cree XLamp LED

(3) Luminous intensity depends on the flux binning and tolerances of the LEDs. Please refer to the Cree

XLamp datasheet for more details on flux binning and mechanical tolerances.

(4) Typical illuminance measured in lux per lumen (E) with typical Cree

7090 XR-E LED. To estimate the

illuminance in lux, multiply the typical illuminance E by the flux in lumen of the LED used. See “Illumination

Calculations” below.

Illumination Calculations

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To calculate peak candela: Find the central spot “on-axis intensity” value in the table above. It is 17

candela/lumen”. Multiply this value by the lumens output from your LED (refer to the XLamp LED

datasheet (

Cree XR-E LED datasheet or Cree XR LED datasheet ) for nominal lumens values. OR for a

more accurate calculation, refer to the intensity binning tables

Cree XLamp binning .

Example – If the Fraen narrow beam reflector # FRC-N1-XR79-0R is use on a cool white Cree XR-E

LED at 350 mA, the typical luminous flux of the LED is 80 lumens:

The calculation is: (17 candela/lumen) x (80 lumens) = 1360 candela peak on-axis.

The central spot

beam angle specified in the table above is 7 degrees full beam-width measured at

half-peak. This means at 3.5 degrees off-axis (half of 7 degrees), the intensity should be half of 1360

candela, or 680 candelas.

1 candela at 1-meter distance produces 1

Lux. This means the peak intensity at 1 meter will be 1360

lux. The intensity decreases as a function of the distance squared, so at 2 meters the peak intensity

will be 1360 / (2

) = 340 lux. At 3 meters distance, the peak intensity will be 1360 / (3

) = 151 lux.

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