Basic Concepts of LED Testing Technology

Today, let's share some basic concepts in LED testing:

Forward voltage: The voltage drop between the two electrodes when the forward current passing through the light-emitting diode is a certain value.

Reverse current: The current flowing through the light-emitting diode when the reverse voltage applied to the two ends of the light-emitting diode is a certain value.

Peak wavelength: The wavelength with the highest spectral radiation power.

Half-intensity angle: In the luminous (or radiant) intensity distribution, the angle formed by the luminous (or radiant) intensity being greater than or equal to half of the maximum intensity.

Dominant wavelength: Any color can be regarded as a color that is matched by mixing a certain spectral color with a reference light source (such as CIE standard light sources A, B, C, etc., isoenergetic light source E, standard illuminant D65, etc.) in a certain proportion. This spectral color is the dominant wavelength of the color. The dominant wavelength of a color is equivalent to the hue (psychological quantity) of the color observed by the human eye. If the chromaticity coordinates of the LED device under test have been obtained, the isoenergetic white light source E (x0 = 0.3333, y0 = 0.3333) can be used as a reference light source to calculate the dominant wavelength of the color. When calculating, according to the slope of the straight line connecting the chromaticity point of the reference light source and the chromaticity point of the sample color on the chromaticity diagram, the intersection of the straight line and the spectral trajectory is read out from the table to determine the dominant wavelength.

Average intensity: The ratio of the luminous flux dΦv contained in a very small solid angle element of a light source in a given direction to this solid angle dΩ, measured in candela (cd).

Radiation bandwidth: The wavelength interval over which the spectral radiation power is greater than or equal to half of the maximum value.

For LED testing, please refer to CIE-127-1997 Measurement of LED: Recommended Standards, and select conditions A and B to measure the average LED specification information under near-field conditions.