How to quickly test the color uniformity of LED lamps? (two)

Back to the origin and use of the SDCM index is not difficult for us to go the way, this is the two similar mathematical proposition, its foundation is a keyword in mathematical statistics theory is used to represent the degree of standard deviation, discrete data set: general calculation steps:

1, for each number and the sample series of the mathematical mean difference, mean that;

2, calculate the difference of each square, said the variance;

3, their sum is then divided by the sample sequence (number -1) by variance

4, open the root get the standard variance!

From the definition of standard variance, we can extend it, and provides a standard definition of chromaticity variance, refers to a lamp, the effective irradiation distance full color mixing spot within the law to take the acquisition of chromaticity coordinates of sample standard variance.

A mixed color light projected on the plane to open, a common application of distance on the uniform meshes of the plane light intensity of 100% to 5% in the intensity region, corresponding to grid points, the use of color meter to collect the chromaticity coordinates, there are n*m sets of data, each set of data for (Xij, Yij), and then input to a calculation table, calculate the average chromaticity coordinates:

Then use the standard deviation formula can be obtained in the form of standard deviation calculation of chromaticity.

Here it can be RGB, or RGBW, or RGBAW, can even color temperature white color combination ACSW.

We use a 3 3WRGB minimum staining light as an example, assume that the distribution of light beam angle is 16 degrees, 33 degrees (50% light intensity) spot angle (10%) light projected onto the 3M far color spot for example, the circular spot of general n=m, so the use of a 11*11 matrix grid collection of various points of CIE rule acquisition

1931 chromaticity coordinates:

Then the corresponding numerical calculation of the average x coordinates and Y coordinates:

The standard deviation of the chromaticity can RGB color mixing lamp:

Reference SDCM