Evaluation of mixed color evenness index - Color standard variance of the test and calculation

With the large-scale application of LED and the new standard GB - 50034, the concept of color tolerance SDCM is more and more into the project bidding documents, lamps and lanterns manufacturer specifications and LED products manufacturer, between pertaining to lamps and lanterns, light color consistency between batches products, not only have to choose the LED BIN, have to do more in-depth to BIN SDCM requirements, general SDCM

SDCM quickly entered the watchful eye of lighting design, more and more people will ask, 'what's your home of lamps and lanterns and light bead SDCM? '

SDCM actual illustration is akin to' a real chromaticity coordinates from another chromaticity coordinates, the relative displacement of typical '.

this metric of raises another not yet on any of the standard another demand 'how to quantitatively evaluate a melange color lamps and lanterns of the homogeneous degree of the spot'.

manufacture of lamps and lanterns manufacturers generally do not reveal the fact is, RGB or RGBW, RGBAW lamps and lanterns of RA chip the size of the luminescence rule and rule of GB of luminescence, and W luminescence rule is different, because light travels in straight lines, in the same lens, RGBAW light path is not a complete overlap. With small red chips, aquamarine blue chip great example, RGB lamp irradiation of light ( Don't discuss the design of the lens itself) General is relatively uniform, in the middle of outer ring partial green.

in general the main factors influencing the color mixture has

1. The size of the chip

2. The number of single LED encapsulation of chip

3. LED the actual packaging style

4. Contains more than just the LED lamps and lanterns of actual shiny surface size and relative relationship of irradiation

5. Choose lens Angle

6. Choose lens and the LED matching

7. There are multiple independent circuit when the uniform distribution of multiple loop

go back to SDCM index of origin and the way of using it is easy to get, this is two similar mathematical proposition, its foundation is a key word - of the theory of mathematical statistics Standard variance, used to represent a data set of discrete degree of general calculation steps for the

1, each number, and the difference between the sample sequence of mathematics average, according to difference;

2, calculate each square, called variance;

3, the sum of them, divided by the sample sequence ( Item number - 1) Get the mean square error

4, square root get standard variance again!

by the definition of standard variance, we can extend it, and a definition of color standard variance, refers to a lamps and lanterns, its effective open fully mixed color light irradiation in law take the acquisition of the chromaticity coordinates of sample standard deviation.

will open a melange of lamps and lanterns, cast in an ordinary application distance of the plane, the plane of the intensity of a light intensity from 100% to 5% area of uniform grid, the grid corresponds to the point, the chromaticity meter on the chromaticity coordinates collection, a total of n * m set of data, for each set of data ( Xij , yij) And then input to a calculation table, calculating the average of chromaticity coordinates,

formula, and then use the standard variance can be calculated in the table of color standard variance.

the eta to RGB, or RGBW, or RGBAW etc. , can even for white light color temperature ACSW mixed color combinations.

we with a minimum 3 star 3 WRGB dyeing project-light lamp, for example, assume that the light distribution of 16 degrees Angle of light beam ( 50% light intensity) 33 degrees flare Angle ( 10%) Light intensity, far mixed color light projected onto the 3 m as an example, the circular light spot generally n = m, so the use of a 11 * 11 matrix grid sampling rule for each point of 1931 CIE chromaticity coordinates,

and then the corresponding numerical calculate average coordinates x and y coordinates:

to the RGB color mixture chromaticity of the standard variance of lamps and lanterns:

reference SDCM

author introduction

Han Baiguang

guangzhou longman photoelectric technical director, global design support center chief designer

the national senior scholars association of lighting designers, Chinese CLDA professional lighting designers association, member of IALD Affiliate member of lighting designers association of North America.

China lighting network original author Han Baiguang