SJ/T 11281-2017 English PDF (SJ/T11281-2017)

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SJ/T 11281-2017: Measure methods of light emitting diode (LED) displays
SJ/T 11281-2017
SJ
ELECTRONICS INDUSTRY STANDARD
ICS 31.120
L 47
Filing No..
Replacing SJ/T 11281-2007
Measure methods of light emitting diode (LED) displays
ISSUED ON. NOVEMBER 07, 2017
IMPLEMENTED ON. JANUARY 01, 2018
Issued by. Ministry of Industry and Information Technology of PRC
Table of Contents
Foreword... 3
1 Scope... 5
2 Normative references... 5
3 Terms, definitions, symbols... 5
4 General requirements... 5
5 Test method... 7
Appendix A (Normative) The slope of the constant dominant wavelength line of the
CIE 1931 chromaticity diagram standard illuminant E (equal energy light source)... 31
Appendix B (Normative) Supporting test software... 35
Measure methods of light emitting diode (LED) displays
1 Scope
This standard specifies the test methods for the mechanical, optical, electrical and other
main technical performance parameters of light-emitting diode (LED) display.
This standard applies to the test of light-emitting diode (LED) display (hereinafter
referred to as display).
2 Normative references
GB 4208 Degrees of protection provided by enclosure (IP code)
SJ/T 11141-2017 Generic specification for LED displays
CIE 1931 Chromaticity diagram
3 Terms, definitions, symbols
The terms, definitions, symbols as established in SJ/T 11141-2017 apply to this standard.
4 General requirements
4.1 Test conditions
4.1.1 Atmospheric conditions
Unless otherwise specified, the test conditions are as follows.
a) Ambient temperature. 15 °C ~ 35 °C;
b) Relative humidity. 20%RH ~ 80%RH;
c) Atmospheric pressure. 86 kPa ~ 106 kPa.
4.1.2 Standard atmospheric conditions for arbitration test
Unless otherwise specified, the standard atmospheric conditions for arbitration test are
as follows.
a) Ambient temperature. 25 °C ± 1 °C;
b) Relative humidity. 48%RH ~ 52%RH;
c) Atmospheric pressure. 86 kPa ~ 106 kPa.
4.1.3 Other environmental conditions
Unless otherwise specified, other environmental conditions shall comply with the
following provisions.
a) AC power supply. (220 ± 22) V, (50 ± 1) Hz;
b) Recommended computer configuration. Mainstream computer hardware
configuration, Windows operating system, graphics card with DVI output;
c) The measurement environment shall be free of mechanical vibration,
electromagnetic, photoelectric interference that may affect the test accuracy;
d) The display shall be debugged to the best state before testing; the configuration
parameters and working state of the display shall not be changed during the test;
e) Before the photoelectric performance test of the display, all light-emitting diodes
shall be lit at 30% of the maximum brightness; the preheating time shall be no
less than 15 minutes.
4.2 Test instruments and software
Unless otherwise specified, the performance of all test instruments shall meet the
specific requirements of the test.
a) Color analyzer (similar instruments for measuring optical properties such as
brightness and chromaticity are also acceptable);
b) Light intensity meter;
c) Illuminance meter;
d) Oscilloscope. Bandwidth not less than DC ~ 100 MHz;
e) Vernier caliper. Graduation value 0.02 mm;
d) Feeler gauge. Graduation value 0.01 mm;
f) Protractor. Graduation value 1°;
g) Steel ruler. Length 1 m;
h) Vibration table. Amplitude greater than 2 mm, resonant frequency 1 Hz ~ 500 Hz,
vibration direction vertical and horizontal;
c) Place the display module to be tested on the bracket; use the geometric center of
the measured area as the axis, to keep the bracket horizontal; rotate it to the left
and right sides respectively, keeping the color analyzer probe always aimed at the
original measured area. When the brightness value drops to LF/2, use a protractor
to measure the angle θSX of the bracket rotation;
d) Measure the horizontal viewing angle of each primary color in the same way; take
the minimum value as the horizontal viewing angle θS of the display.
5.2.2.4.2 Vertical viewing angle
Measure as follows.
a) Place the LED on a bracket by rotating it 90° clockwise facing the LED emitting
surface;
b) Same as 5.2.2.4.1.a);
c) Same as 5.2.2.4.1.b);
d) Same as 5.2.2.4.1.c);
e) Measure the vertical viewing angle of each primary color in the same way; take
the minimum value as the vertical viewing angle θC of the display.
5.2.3 Maximum contrast
5.2.3.1 Purpose
Measure the maximum contrast of the display under specified conditions.
5.2.3.2 Measurement principle
Same as 5.2.1.
5.2.3.3 Measurement conditions
The measurement conditions are as follows.
a) The illuminance in the normal direction of the indoor display is 10 × (1 ± 10%)
lx;
b) The illuminance in the normal direction of the outdoor display is 5000 × (1 ± 10%)
lx;
c) The acquisition range of the color analyzer shall not be less than 16 adjacent pixels.
5.2.3.4 Measurement steps
g) The maximum value is the brightness uniformity LMJ of the display module of the
screen.
5.2.7.3 Display module brightness uniformity
5.2.7.3.1 Purpose
Measure the brightness consistency between modules in the same display.
5.2.7.3.2 Measurement principle
Same as 5.2.1.2.
5.2.7.3.3 Measurement conditions
The measurement conditions are as follows.
a) The change in ambient illumination is less than ±10%;
b) The acquisition range of the color analyzer shall not be less than 16 adjacent pixels.
5.2.7.3.4 Measurement steps
Measurement is carried out according to the following steps.
a) During the measurement process, the angle between the observation line and the
display remains unchanged;
b) 9 display modules are randomly selected within the full screen range (9 display
modules are randomly selected in the black screen state);
c) At the highest grayscale level and the highest brightness level, a primary color is
displayed on the full screen;
d) The brightness values of the 9 display modules are measured by a color analyzer;
then the arithmetic mean is calculated;
e) The brightness uniformity LMJ of the primary color display module of the display
is calculated by formula (9).
Where.
LMJ - Brightness uniformity of the display module;
L - Brightness of the display module, in candela per square meter (cd/m2);
- Arithmetic mean of the brightness of the 9 display modules, i.e.
, in candela per square meter (cd/m2).
f) Using the same method, measure and calculate the three primary colors of red,
green, blue respectively;
g) The maximum value is the brightness uniformity LMJ of the display module of the
screen.
5.3 Electrical performance
5.3.1 Frame frequency
5.3.1.1 Purpose
Measure the update frequency of the screen information on the display.
5.3.1.2 Measurement principle
Make a special test video, which sets different graphics frame by frame. The number of
different graphics that can be displayed on the display is the frame frequency.
5.3.1.3 Measurement conditions
The measurement conditions are as follows.
a) The size of the display meets the requirements of the test software
b) The computer installed with test software outputs graphics to the display.
5.3.1.4 Measurement steps
Perform the measurement as follows.
a) Start the test software; select the frame rate test function (see Appendix B); set an
area on the display, so that the image can be displayed on the display;
b) Start the test software on the display; record the graphics being displayed on the
display. The refresh frequency FH is equal to the number of graphics displayed FF,
that is, FH = FF.
5.3.2 Refresh frequency
5.3.2.1 Purpose
Measure the number of times the display data is repeated per second on the display.
f) Calculate the refresh rate FC by formula (10).
FC - Refresh rate, in Hertz (Hz);
T - Period of the waveform, in seconds (s).
5.3.3 Grayscale
5.3.3.1 Purpose
Measure the brightness change level of the display from zero grayscale to the highest
grayscale.
5.3.3.2 Measurement principle
The calibrated grayscale levels are generally divided into no grayscale, 4-level
grayscale, 8-level grayscale, 16-level grayscale, 32-level grayscale, 64-level grayscale,
128-level grayscale, 256-level grayscale, 1024-level grayscale, 4096-level grayscale,
etc. In any grayscale level, the brightness increases monotonically with the increase of
the grayscale level.
5.3.3.3 Measurement conditions
The measurement conditions are as follows.
a) The ambient illumination change rate is less than ±10%;
b) The acquisition range of the color analyzer shall not be less than 16 adjacent pixels;
c) The acquisition range of the color analyzer remains unchanged during the entire
test process.
5.3.3.4 Measurement steps
Measurement is carried out according to the following steps.
a) Start the test software; select the grayscale test function (see Appendix B);
increase the grayscale level step by step; the brightness of the display shall
increase monotonically with the increase of the grayscale level;
b) The actual grayscale level is in accordance with the following provisions.
If. 1 < G ≤ 2, the display has no grayscale;
If. 2 < G ≤ 4, the display has 4-level grayscale;
If. 4 < G ≤ 8, the display has 8-level grayscale;
level of the transformation; the color analyzer is used to measure the brightness
value L1;
b) The display brightness is set to the highest level; the grayscale is set to the second
level of the transformation; the color analyzer is used to measure the brightness
value L2;
c) The display brightness is set to the highest level; the grayscale is set to the highest
level; the color analyzer is used to measure the brightness value Lm.
The signal processing depth Sd is calculated by formula (11).
Where.
Sd - Signal processing depth;
L1 - Brightness of the display at 1-level grayscale, in candela per square meter
(cd/m2);
L2 - Brightness of the display at 2-level grayscale, in candela per square meter
(cd/m2);
Lm - Brightness of the display at the highest grayscale, in candela per square meter
(cd/m2).
Note. In formula (10), < > means rounding off and taking integer.
5.3.5 Pixel out-of-control rate
5.3.5.1 Purpose
Measure the out-of-control pixels on the display.
5.3.5.2 Measurement principle
Identify the out-of-control pixels on the display by visual inspection; calculate the pixel
out-of-control rate.
5.3.5.3 Measurement conditions
Drive the LED display normally.
5.3.5.4 Measurement steps
5.3.5.4.1 Entire screen pixel out-of-control rate
Measurement is performed as follows.
a) Display the highest grayscale red on the entire screen; visually count the number
of pixels that are not lit PF;
b) Display a full black screen signal; visually count the number of red pixels that are
always lit PL;
c) Calculate the red pixel out-of-control rate PZR using formula (12).
Where.
P - Total number of pixels on the entire screen (if P is less than 10000, it is calculated
as 10000), in pcs;
PF - Number of pixels that are not lit, in pcs;
PL - Number of pixels that are always lit, in pcs.
d) The same method can be used to calculate the blue pixel out-of-control rate PZB
and the green pixel out-of-control rate PZG;
e) The highest value among PZR, PZB, PZG is the entire screen pixel out-of-control
rate PZ.
5.3.5.4.2 Regional pixel failure rate
Measure as follows.
a) Start the test software; select the pixel failure rate test function (see Appendix B);
set a 100 × 100 pixel movable red square (highest grayscale);
b) Move the square to find the area Ap with the densest red blind spots;
c) Count the number of red blind spots M in the square by visual inspection;
d) Display a black screen; count the number of red bright spots N in the area Ap by
visual inspection;
e) The regional red pixel failure rate is equal to the sum of M and N divided by the
number of regional pixels (PQR = (M + N)/10000);
f) The regional green pixel failure rate PQG and the regional blue pixel failure rate
PQB can be calculated by the same method;
g) The highest value among PQR, PQB, PQG is the regional pixel failure rate PQ.
5.3.6 Automatic adjustment of display brightness
5.3.6.1 Purpose
Measure the ability of the display brightness to adjust as the ambient brightness changes.
5.3.6.2 Measurement principle
The automatic brightness adjustment function of the display is to sense the ambient
illumination through a photoelectric sensor and feed it back to the display controller for
brightness adjustment.
5.3.6.3 Measurement conditions
The measurement conditions are as follows.
a) The ambient illumination change rate is less than ±10%;
b) The acquisition range of the color analyzer shall not be less than 16 adjacent pixels;
c) The acquisition range of the color analyzer shall remain unchanged throughout
the test.
5.3.6.4 Measurement steps
Perform the measurement as follows.
a) Place the display under a certain ambient illumination; adjust the brightness of the
screen to the maximum value;
b) Use a color analyzer to measure and record the brightness of the display;
c) Use a illuminance meter to measure artificial light;
d) For the light sensor probe of the display, project artificial light; adjust it to greater
than 10000 lx to measure the brightness of the display;
e) For the light sensor probe of the display, project artificial light; adjust it to greater
than 1000 × (1 ± 20%) lx to measure the brightness of the display;
f) For the light sensor probe of the display, project artificial light; adjust it to greater
than 100 × (1 ± 20%) lx to measure the brightness of the display;
g) For the light sensor probe of the display, project artificial light; adjust it to greater
than 10 × (1 ± 20%) lx to measure the br...