IEC 62595-2-1 Display lighting unit -Part 2-1: Electro-optical measuring methods of LED backlight unit

Scope

This part of IEC 62595 specifies the standard measurement conditions and measuring methods for determining the electrical and optical parameters of LED backlight units for liquid crystal displays.

Normative references

The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

IEC 61747-30-1, Liquid crystal display devices – Part 30-1: Measuring methods for liquid crystal display modules – Transmissive type

IEC 62595-1-2, Display lighting unit – Part 1-2: Terminology and letter symbols 1

Terms and definitions

For the purposes of this document, the terms and definitions given in IEC 62595-1-2 apply.

Abbreviations

BLU backlight unit

FOV field of view

LMD light measuring device

LSF light spread function

Luminance

The measurements should be carried out in the dark room under the standard measuring conditions and for the design viewing directions, as follows:

a)Position the BLU.

b) Adjust the LMD to the specified viewing direction, according to angles 0 and .

c) Supply the value of the input signals to the BLU. Then measure the BLU at position p, to obtain the luminance L (0,φ). (In case of i=0, the position implies the centre of the active area of the BLU.)

The LMD should be carefully checked before measurements, considering the following
elements:
sensitivity of the measured quantity to the measuring light;

errors caused by veiling glare and lens flare (i.e., stray light in an optical system);

timing of data-acquisition, low-pass filtering and aliasing-effects;

linearity of detection and data-conversion;

measurement size and field of view (FOV).

To ensure luminance accuracy for the intended LED sources, a broad bandwidth LMD should be calibrated using a spectrometer with a bandwidth 5 nm or less.

The luminance of BLU should be measured by synchronizing the LMD with the BLU refresh rate, or integrating the measured luminance over a number of frames.

Chromaticity

CIE 1931 chromaticity coordinates (IEC 60050-845:1987, 845-03-28 [3] and ISO 11664-1 [4]), x, y, z on the BLU surface of the active area are obtained using the tristimulus values, X, Y, Z calculated from measured spectral power distribution S(2) given in 5.2.4 (see IEC 62595-1-2). The correlated colour temperature (CCT) can also be used.

NOTE Correlated colour temperature (CCT) is defined in IEC 60050-845:1987, 845-03-50. The calculation method from the measured chromaticity data is specified in CIE publication 15:2004 [5]. Robertson’s [6] procedure is available for an actual computing program.

This measurement is carried out usually on on the axis normal to the surface of the BLU, however, other angles can also be considered for certain purposes.

LISUN following instruments fully meet IEC 62595-2-1 Display lighting unit -Part 2-1: Electro-optical measuring methods of LED backlight unit:

XYL-VI Luminance Colorimeter

LS-ELF 2D Video Luminance Meter