What is color difference SDCM and how to do the measurement?

Color difference is an important indicator of lighting lamps color performance. Color difference is the difference between computer calculation forma and the target standard, calculated by single lighting source, the value is smaller, accuracy is higher. Please note, it only represents the compared color of a light source, it can not detect the deviation under different light sources. Generally speaking, color difference refers to the distance that the measurement value deviates from the target value, the difference between the light source spectrum and the standard spectrum. It needs provide the target value and calculation formula to know the measurement value of color difference. It can be tested by the colorimeter integrated sphere.

Standard spectrum changes with color temperature, the color difference is different for the same light source if the standard spectrum is different, but when test, general color photoelectric analysis system can automatically identify the color temperature range where the measured light source is, to determine the color temperature value of standard spectrum. When the color temperature is same, reference standard spectrum is consistent, chromaticity coordinate X,Y is different, the color difference is also different.

Color difference unit: SDCM. National standard has its specific testing requirement, IEC 60901 and GB-T17262 single-ended fluorescent lamp performance requirements specified in the standard that general energy-saving lamps require color tolerance less than 5 SDCM. IEC 62717 and GB24823 general lighting for LED modules performance requirements specified in the standard that LED modules require color difference less than 7SDCM. In the ellipse of 5SDCM, color difference is 5 if the point is on the curve of ellipse, color difference is less than 5 if the coordinates is in the circle of ellipse. IEC standard requires that the lamp chromaticity coordinate(x,y) should not deviate the rated value from 5SDCM, that is to say, the chromaticity coordinate of lamp should be in the ellipse, the color difference should be less than 5 SDCM for general energy-saving lamps. For color difference ellipse diagram, outer ring is 6SDCM corresponding to the national standard, inner ring is 5SDCM corresponding to international standard. Industry standard, Energy Star ANSI C78.376, Color Difference≤7SDCM; EU Standard IEC60081, Color Difference≤7SDCM; National Standard GB10682-2002, Color Difference≤5SDCM.

In the fluorescent lamp, as the density of red, green and blue powder is different, it is easy to cause color temperature difference in production. Once appear, it needs adjust color difference to adjust color temperature difference to ensure light color of light. White LED as light source, it should refer to color difference standard requirement to guide the development and application of white LED new lighting source. 

Lisun Group’s LPCE-2(LMS-9000) integrating sphere & spectroradiometer system and LMS-6000 Portable CCD Spectroradiometer can measure SDCM and are widely applied to Luminaries manufacturing enterprise and lab, such as Sharp Electronics in Memphis TN(USA), PT. SHARP SEMICONDUCTOR INDONESIA (Indonesia), TUV Rheinland InterCert Kft.( Hungary), Philips Lighting(Netherlands), Sony Semiconductor Corporation etc. 

Here is the software surface of LPCE-2:

What Is Color Difference SDCM And How To Do The Measurement

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