Background Statement for SEMI Draft Document 5291A New Standard: TEST METHOD OF AMBIENT COLOR GAMUT FOR FPD UNDER INDOOR ENVIRONMENTS Notice: This background statement is not part of the balloted item. It is provided solely to assist the recipient in reaching an informed decision based on the rationale of the activity that preceded the creation of this Document. Notice: Recipients of this Document are invited to submit, with their comments, notification of any relevant patented technology or copyrighted items of which they are aware and to provide supporting documentation. In this context, patented technology is defined as technology for which a patent has issued or has been applied for. In the latter case, only publicly available information on the contents of the patent application is to be provided. Background Displays are usually used under indoor environments such as office and living rooms. And the measurement results of display color gamut are affected by various issues such as types and directions of illuminant. Therefore, it is necessary to standardize the test methods to evaluate ambient color gamut under indoor environments for FPD. The results of this ballot will be adjudicated at the Taiwan Flat Panel Display Committee meeting scheduled on 24 th Oct, 2012 in Hsinchu, Taiwan. If you have any question, please do not hesitate to contact Ambient Color Gamut Task Force co-leaders: Tony Wang, tony1.wang@chimei-innolux.com Samper Wang, samperwang@itri.org.tw Shiang-Yuan Pan, Garfield.Pan@auo.com Or SEMI Staff, Catherine Chang, cchang@semi.org
SEMI Draft Document 5291A New Standard: TEST METHOD OF AMBIENT COLOR GAMUT FOR FPD UNDER INDOOR ENVIRONMENTS 1 Purpose 1.1 Displays are usually used under indoor environments such as office and living rooms. And the measurement results of display color gamut are affected by various issues such as types and directions of illuminant. Therefore, it is necessary to standardize the test methods to evaluate ambient color gamut under indoor environments for flat panel displays (FPD). 2 Scope 2.1 This standard is applicable to ambient color gamut measurement for flat panel displays (FPD). NOTICE: This standard does not purport to address safety issues, if any, associated with its use. It is the responsibility of the users of this standard to establish appropriate safety and health practices and determine the applicability of regulatory or other limitations prior to use. 3 Limitations 3.1 This standard is applicable to ambient color gamut measurement for transmissive type FPD under diffuse lighting. The ambient color gamut measurement under direct lighting does not include in this standard. 3.2 This standard is applicable to transmissive type FPD for indoor use only. 4 Referenced Standards and Documents 4.1 SEMI Standard SEMI D56 Measurement Method for Ambient Contrast of Liquid Crystal Displays 4.2 CIE Standard 1 CIE 15:2004 3rd edition Colorimetry 4.3 VESA Standard 2 FPDM 2.0 Flat Panel Display Measurements Standard NOTICE: Unless otherwise indicated, all documents cited shall be the latest published versions. 5 Terminology 5.1 Abbreviations and Acronyms 5.1.1 FPD Flat Panel Display 5.1.2 LMD Light Measurement Device 5.1.3 DUT Display Under Test 5.1.4 CCT Correlated Color Temperature 5.2 Definitions 5.2.1 Ambient color gamut color gamut of display measured under ambient lighting condition. 5.2.2 Sampling port the port of the integrating sphere which light exits from and hits on the DUT, it confines the sampling area of the DUT. 1 International Commission on Illumination, http://www.cie.co.at/ 2 Video Electronics Standards Association, http://www.vesa.org/ Page 1
5.2.3 Measurement port the port of the integrating sphere which the beam of the LMD is aligned through it to focus on the surface of DUT. 5.2.4 Specular port the port of the integrating sphere which is on the opposite side of and symmetrical to the measurement port. 6 Summary of Test Method 6.1 Environment Conditions Temperature: 25 ± 3 C Humidity: 40% to 60% RH Illumination of surrounding: dark room 1 lx No reflection or low reflection objects of surroundings 6.2 Measurement Setup 6.2.1 A uniform diffuse-ambient light is provided by a light source with an integrating sphere to illuminate the screen of the display (see Figure 1). The DUT is placed against the sampling port of the integrating sphere. The LMD is arranged to view the screen through the measurement port. LMD specular port measurement port integrating sphere 8 lamp sampling port DUT Figure 1 The Measurement Configuration 6.3 Measurement Conditions 6.3.1 The luminance uniformity at the sampling port of the integrating sphere is better than 95%. NOTE 1: To determine the luminance uniformity is to measure the uniform source at its center and then eight other places (top, bottom, left, right, and the diagonals) from 75 % to 80 % of the radius from the center to the edge of the sampling port. 6.3.2 The integrating sphere has one sampling port, one measurement port and one specular port (open or close situation). The angle from center of the measurement port to the normal of the DUT is 8 (± 2 ). Page 2
6.3.3 The LMD is focused on the display surface. 7 Apparatus 7.1 Uniform Diffuse Light Source Use a lamp with an integrating sphere to provide a uniform diffuse-ambient light. 7.2 Light Measurement Device Use a colorimeter or spectroradiometer to measure the luminance and color. Use an illuminance meter to measure the illuminance on the surface of DUT. If the illuminance on the screen cannot be measured with the illuminance meter directly, a diffuse white reflectance standard of known reflectance or a detector with known response to illuminance shall be used. 8 Input Signals 8.1 Following 8.2 a) to 8.2 f) full screen input signals are defined and used. 8.2 List of input signals (see Figure 2) a) Red (R): Input signal with the level 100 % R, 0 % G and 0 % B, b) Green (G): Input signal with the level 0 % R, 100 % G and 0 % B, c) Blue (B): Input signal with the level 0 % R, 0 % G and 100 % B d) Cyan (C): Input signal with the level 0 % R, 100 % G and 100 % B e) Magenta (M): Input signal with the level 100 % R, 0 % G and 100 % B f) Yellow (Y): Input signal with the level 100 % R, 100 % G and 0 % B Red Green Blue Cyan Magenta Yellow Figure 2 Full-Screen Red, Green, Blue, Cyan, Magenta and Yellow Input Color Signals 9 Preparation of Apparatus 9.1 Warm up the measuring equipment for a specified period of time to stabilize (according to the instruction manual of measuring equipment). 10 Calibration and Standardization 10.1 The LMD used for light source characteristics, color and illuminance measurements shall be calibrated and traced to the accredited laboratory. Page 3
11 Procedure 11.1 Measurement With the Specular Port Closed 11.1.1 Turn on the DUT, and the warm-up time shall be enough to allow the DUT to reach a stable luminance level (assessed by a luminance instability of 5% per hour of operation or less using a white full-screen center measurement of the luminance). After being turned on, the DUT and all associated electronics need to reach a level of stability before the light output from the DUT is stable. 11.1.2 Set up the integrating sphere and turn on its lamp to warm up the light source for a specified period of time to stabilize (according to the instruction manual of measuring equipment). 11.1.3 The illuminance is adjusted to the required levels by controlling the intensity of the light source. It is important to keep the CCT of the light source stable during the illuminance adjustment. 11.1.4 Apply full-screen input color signals (see Figure 2) to the DUT. 11.1.5 Measure the CIE 1976 UCS (uniform chromaticity scale) chromaticity coordinates (u R, v R ), (u G, v G ), (u B, v B ), (u C, v C ), (u M, v M ), and (u Y, v Y ) for R, G, B, C, M, Y signals at the center point on the DUT screen, respectively. 11.2 Measurement With the Specular Port Opened 11.2.1 Warm up the DUT to required stability. 11.2.2 Set up the integrating sphere and turn on its lamp to warm up the light source for a specified period of time to stabilize (according to the instruction manual of measuring equipment). Remove the cover of the specular port. 11.2.3 The illuminance is adjusted to the required levels by controlling the intensity of the light source. It is important to keep the CCT of the light source stable during the illuminance adjustment. 11.2.4 Apply full-screen input color signals (see Figure 2) to the DUT. 11.2.5 Measure the CIE 1976 UCS (uniform chromaticity scale) chromaticity coordinates (u R, v R ), (u G, v G ), (u B, v B ), (u C, v C ), (u M, v M ), and (u Y, v Y ) for R, G, B, C, M, Y signals at the center point on the DUT screen, respectively. An example of measuring results at illuminance of 500 lx is shown in Figure 3. Figure 3 Example of Measuring Results at Illuminance of 500 lx NOTE 2: The illuminance of 200 lx and 500 lx are typical for a bright living room and an office environment. NOTE 3: If the measurement equipment gives the CIE (x, y) values, transform each of the (x, y) pairs to (, ), using the following equations: = 4x/(3 + 12y - 2x), = 9y/(3 + 12y - 2x) Page 4
12 Calculations or Interpretation of Results 12.1 Draw a hexagon with six vertices P R (u R, v R ), P Y (u Y, v Y ), P G (u G, v G ), P C (u C, v C ), P B (u B, v B ), and P M (u M, v M ) ordered according to counterclockwise orientation on the chromaticity diagram for calculation of color gamut (see Figure 4). 12.2 Compute the area of the hexagon compassed by P R, P Y, P G, P C, P B, P M six points. The total area A is calculated according to eq. (1). P G P Y P R P C P M P B Figure 4 Area of Hexagon for Color Gamut Calculation A 1 2 R Y R Y Y G Y G G C G C C B C B B M B M M R M R (1) 12.3 Divide the total area A by 0.1952 and multiply by 100 % to obtain the color gamut. NOTE 4: The value of 0.1952 is the area inside spectrum locus in CIE 1976 UCS chromaticity diagram. NOTE 5: To obtain the color gamut of NTSC in (u v) space, divide the total area A by 0.07407 and multiply by 100 %. The three primary RGB coordinates of NTSC in CIE 1931 (x, y) and CIE 1976 UCS (, ) chromaticity diagram are listed in Table 1. Table 1 The RGB Coordinates of NTSC in CIE 1931 (X, Y) and 1976 (U', V') Chromaticity Diagram (x R, y R ) (x G, y G ) (x B, y B ) (0.67, 0.33) (0.21, 0.71) (0.14, 0.08) ( R, R ) ( G, G ) ( B, B ) (0.48, 0.53) (0.08, 0.58) (0.15, 0.20) Page 5
13 Report 13.1 The measurement results are reported as given in Table 2. Table 2 Example of Ambient Color Gamut Measurement Results Display model no. TEST 1001 Specular port open close Light source/cct Illuminance Standard illuminant source A/2856K 500 lx CIE 1976 (u v ) R G B u R v R u G v G u B v B 0.4133 0.5217 0.1328 0.5538 0.1767 0.2584 C M Y u C v C u M v M u Y v Y 0.1429 0.4549 0.2862 0.3675 0.2112 0.5456 Color gamut (%) 22.0% (or 58% NTSC) 14 Related Documents Edward F. Kelley, Diffuse Reflectance and Ambient Contrast Measurements Using a Sampling Sphere. Proceedings of the Third Americas Display Engineering and Applications Conference (ADEAC), Society of Information Display (2006): pp.1 5. Yu-Ping Lan, Shiang-Yuan Pan, Tong-Sheng Mou and Yingying Xu, P-66: Measurement Comparison of Ambient Contrast for Liquid Crystal Displays. SID 10 DIGEST, Society of Information Display (2010): pp.1497 1499. NOTICE: (SEMI) makes no warranties or representations as to the suitability of the Standards and Safety Guidelines set forth herein for any particular application. The determination of the suitability of the Standard or Safety Guideline is solely the responsibility of the user. Users are cautioned to refer to manufacturer s instructions, product labels, product data sheets, and other relevant literature, respecting any materials or equipment mentioned herein. Standards and Safety Guidelines are subject to change without notice. By publication of this Standard or Safety Guideline, SEMI takes no position respecting the validity of any patent rights or copyrights asserted in connection with any items mentioned in this Standard or Safety Guideline. Users of this Standard or Safety Guideline are expressly advised that determination of any such patent rights or copyrights, and the risk of infringement of such rights are entirely their own responsibility. Page 6
RELATED INFORMATION 1 AN EXAMPLE OF COLOR GAMUT MEASUREMENT AT DIFFERENT DIFFUSE LIGHTING CONDITIONS NOTICE: This Related Information is not an official part of SEMI [designation number] and was derived from the work of the global [committee name] Technical Committee. This Related Information was approved for publication by full letter ballot procedures on [A&R approval date]. R1-1 Experimental Equipment R1-1.1 Use a lamp with an integrating sphere (light source) providing a uniform diffuse-ambient light to illuminate the screen of a liquid crystal display (LCD). R1-1.2 Use a light measurement device (LMD), a colorimeter or a spectroradiometer, to measure the color of the LCD. R1-1.3 Use an illuminance meter to measure the illuminance on the surface of LCD. R1-1.4 The illuminance is adjusted to the required levels by controlling the intensity of the light source. R1-2 Experimental Set-up R1-2.1 The LCD is placed against the sampling port of the integrating sphere. R1-2.2 The LMD is arranged to view the screen through the measurement port of the integrating sphere. R1-3 Measurement Procedure R1-3.1 Set the illuminance = 0 lx. R1-3.2 Apply full-screen R, G, B, C, M, and Y input color signals on the LCD screen. R1-3.3 Measure the chromaticity coordinates in CIE 1976 UCS (u, v) color space for R, G, B, C, M, Y signals at the center point on the LCD screen. R1-3.4 Calculate the color gamut. R1-3.5 Adjust the illuminance to the required levels. R1-3.6 Repeat R1-3.2 to R1-3.6. The illuminance is adjusted from 0 lx to 1000 lx with step 100 lx. R1-4 Experimental Results R1-4.1 The measurement results of the CIE 1976 UCS chromaticity coordinates for R, G, B, C, M, Y signals at illuminance of 1000 lx are shown in Figure R1-1. Page 7
Figure R1-1 Measurement Results at Illuminance Of 1000 lx R1-4.2 The area ratio defined as below at different illuminance are computed. area of hexagon RGBCMY Area ratio (2) area of triangle RGB The hexagon and the triangle are formed by measurement results of R, G, B, C, M, Y signals and by measurement results of R, G, B signals in (, ) space. The results are shown in Table R1-1 and Figure R1-2. The area ratio is increased linearly with the increase of illuminance. Table R1-1 Area Ratio at Different Illuminance Illuminance (lx) Area Ratio 0 1.005 100 1.011 200 1.021 300 1.033 400 1.046 500 1.058 600 1.067 700 1.076 800 1.087 900 1.096 1000 1.104 Page 8
Area Ratio LETTER (YELLOW) BALLOT 1.12 1.1 1.08 1.06 1.04 1.02 1 0.98 R 2 = 0.9964 0 100 200 300 400 500 600 700 800 900 1000 Illuminance (lx) Figure R1-2 Measurement Results at Illuminance of 1000 lx Page 9