C-Parameters: A New Way to Describe Color

C-Parameters are an expression of the spectral power distribution in a set of real-numbers, breaking down major color components of the photonic emission of light emitting devices into quantifiable metrics. C-Parameters quantify color, so math can be done on color.

White Paper- C-Parameters Intro

What are C-Parameters?


A warm white LED with a CCT of 3000K has a SPD (spectral power distribution) like the one above. The spectral power distribution tells of the amount of power at various wavelengths per unit of area of light.


The C-Parameters of the white LED are the number representations of the Gaussian components that add together to recreate the white LED SPD. A CPA, CPC, CPW number represents the amplitude, center wavelength, and width, respectively, of each of the Gaussian components, thus breaking down the whole SPD into a compact, quantifiable, measurable, comparable metric. (U.S. Patent No. 9128144, 9279725)

C-Parameter Pros

Unlike Dominant wavelength or centroid, which attempt at providing a single measure for a LED by integrating or convolving the spectrum, C-parameters characterizes the full spectrum and the shape of the SPD. When only using single point metrics, data slips through the cracks.

For quantifying single colored LED's, peak Power, FWHM (full-width half-max), and peak Wavelength are used to characterize the SPD. However, it fails to fully capture what is going. For an example, see below.

Why C-Parameters?


If only a single Gaussian is used to characterize a LED spectrum, it simply does not fit reality.

Pictured above is a blue LED, and a whole region from 442nm to 500nm is not characterized.


However, with C-Parameters, the CP SPD (the sum of the Gaussian components) fully fits the blue LED spectrum to an R^2 = 0.999865.

C-Parameter Features

C-Parameters are tied to the physics not color perception. Therefore even non-visible LED's (UV, or IR) can use C-Parameters as a metric.

Finite and meaningful analysis can be done for detecting and tracking process variations and defects in each stage of the LED manufacturing process.

Specific light generating mechanisms, band gap emission, phosphors, color transforming of light by the package or lenses can be now measured, quantified and analyzed using C-Parameters.


LED Manufacturing - Yield tracking and yield improvement

UV, IR, non-visible LED characterization

Analysis of LED use cases and selection or binning criteria for scientific applications

Read our case study about detecting outliers in this specific sensor application:

Case Study: Outliers

Op-Test patented technology:
US Patent No. 9,128,144, 9,279,725 Aus Pat. No. 2011289628, Taiwan Pat. No. I545305, and other patents pending.