light intensity equation with wavelength

LIGHT INTENSITY EQUATION WITH WAVELENGTH HOW TO

Or equivalently the ratio of luminous intensity I v in lumens/sr (or candelas) to radiant intensity I e in watts/sr.

Where the definition is the ratio of luminous (or visible) flux Φ v in lumens to radiant flux Φ e in watts, The relevant conversion factor is called the luminous efficacy K: However for LEDs with a relatively narrow band of emission wavelength, the conversionįrom photometric units (millicandelas) to radiant units (mW/sr) is relatively easy as described below. Involving weighing the human eye response with the actual spectral intensity output of the source. Of an ideal black-body radiator at a specific temperature weighted with the response of the human eye, conversion of an arbitrary optical source from luminous to radiant units requires a calculation Since photometric units are based on a standard

LIGHT INTENSITY EQUATION WITH WAVELENGTH HOW TO

mA/mW) so it is convenient to understand how to convert LED intensity specifications between systems. However, photodiode sensitivity is often specified in terms of red, green, white) use the luminous (photometric) units while infrared LEDs use radiant units. Usually LEDs emitting in the visible (e.g. However usually places more radiant intensity into a narrower radiation pattern. The design of real LEDs (chip design and packaging reflectors etc.) Was a planar Lambertian emitter (perfectly diffuse source), the half-intensity angle would be 60 degrees (Lambert's cosine law). The bright center spot is the main radiation field with an intensity half-width of about 15 degrees. A typical radiation fieldįrom a high-radiance red LED is shown to the right. Some LED specification sheets provide a plot showing how the radiation intensity pattern depends on direction angle θ. The steradian (sr) is the unit of solid-angle measurement. 20 mA) and at the peak of the forward emission radiation pattern.

(mcd = millicandelas = millilumens per steradian = mlm/sr) at a typical forward current (e.g. Light emitting diodes (LED) have output intensities that are specified in two types of units: radiant intensity (mW/sr = milliWatts per steradian) and luminous intensity (photometric units)

Light intensity equation with wavelength