Iec 61747 30 1 2012

3.2 Abbreviations CFF critical flicker frequency CR contrast ratio CRPF Plain Field Contrast Ratio DUT device under test FFT fast Fourier transform GSI gray-scale inversion HXT horizont

Terms and definitions

For the purposes of this document, the terms and definitions given in IEC 60050-845:1987 apply

NOTE Several points of view with respect to the preferred terminology on "monochrome", "achromatic",

In the fields of spectroscopy, physics, and engineering, terms like "chromatic," "colour," and "full-colour" are commonly used to describe the chromaticity of displays All LCDs exhibit some form of chromaticity influenced by factors such as viewing angle and ambient temperature Until a detailed official definition is established, the term "chromaticity" will refer to the colour capabilities of displays that users can address electrically According to IEC 61747-6-2, a monochrome display lacks user-addressable chromaticity, while a colour display offers at least two user-addressable colours A full-colour display, on the other hand, includes a minimum of three primary colours, each with at least 6 bits, allowing for over 260,000 distinct colours.

Abbreviations

CR PF Plain Field Contrast Ratio

LNU long range non-uniformity

General comments and remarks on the measurement of transmissive LCDs

Transmissive LCDs utilize integrated backlight illumination to display visual information, but achieving consistent and reproducible measurement results can be challenging due to the close interaction between the backlight system, the LMD, and the DUT When the backlight unit is dynamic, it is crucial to understand its behavior and ensure that measurements are conducted without interference from backlight variations, such as those caused by PWM signals or dynamic adjustments To ensure accuracy, the luminance and color of the backlight must be specified, and its operation should remain static and stable throughout the measurement period.

The backlight luminance must exhibit a temporal drift of less than 5% per hour and under 1% per minute from its stabilized value It is essential to ensure that the temperature of the Device Under Test (DUT) is stable and not influenced by the backlight illumination system.

Constant and correct temperature of the DUT should be verified

For optimal illumination of the Device Under Test (DUT) without a built-in light source, the backlight luminance or illuminance must remain stable within ± 1% and free from short-term fluctuations such as ripple or PWM To achieve this, an equilibration period of 5 to 10 minutes is necessary, and it is essential to verify that the temperature of the DUT remains constant and accurate.

Viewing-direction coordinate system

The viewing-direction refers to the angle from which an observer examines a specific spot on the Device Under Test (DUT) In measurements, a light-measuring device simulates the observer's perspective, focusing on a designated area on the DUT This viewing-direction is defined by two angles: the angle of inclination θ, which relates to the surface normal of the DUT, and the azimuth angle φ The azimuth angle is analogous to a clock face, where φ = 0° corresponds to the 3 o'clock position ("right"), φ = 90° to the 12 o'clock position ("top"), φ = 180° to the 9 o'clock position ("left"), and φ = 270° to the 6 o'clock position ("bottom").

Figure 1 – Representation of the viewing-direction (equivalent to the direction of measurement) by the angle of inclination, θ and the angle of rotation (azimuth angle), φ in a polar coordinate system

Standard illumination geometries

Transmissive LCD modules typically include integrated light sources, which are constrained by their positioning relative to the device under test (DUT) and the measurement equipment Each system operates within a dark measuring room, ensuring that the illuminance on the DUT, not produced by the built-in light source, remains below 1 lx This low light level is crucial to prevent significant interference with the measurement results.

Throughout this standard it is assumed the DUT is provided with its own, integrated backlight

If the Device Under Test (DUT) lacks its own illumination source, external lighting must be provided in one of three ways: a) using a diffuse light source with specified luminance and spectrum positioned behind the DUT, suitable for direct view display measurements; b) employing a point light source that is geometrically small and homogeneous, ensuring alignment between the light source, measurement spot, and detector, with the detector focused on the DUT's measurement spot; or c) utilizing a directional light source that offers calibrated spatial uniformity of illumination at the DUT's plane, with an illumination angle of less than 30° and, if necessary, a calibrated spectral intensity distribution in the visible range, primarily for projection-display module measurements.

For all three scenarios, it is essential to include detailed specifications of the light source, such as intensity distribution, temporal stability, and opening angle, along with its distance to the Device Under Test (DUT) It is advisable to utilize light sources that closely resemble illuminant D65.

5 Standard measurement equipment and set-up

Light measuring devices (LMD)

The light measuring devices (LMDs) used for evaluation of the optical properties of transmissive LCDs shall be checked for the following criteria and specified accordingly:

• sensitivity of the measured quantity to polarization of light;

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

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

• linearity of detection and data-conversion.

Positioning and alignment

The LMD must be strategically positioned in relation to the measurement field on the DUT to enable adjustments in both the measurement direction and the distance from the center of the measuring spot, ensuring an angular aperture of less than 5° This adjustment can be achieved through a mechanical system, often motorized, or by utilizing an appropriate optical system, such as conocopic optics.

Standard measurement arrangements

LMD conditions

To determine the angular aperture of the LMD when it is not specified, one can calculate it using the distance from the LMD to the measurement field along with the LMD's aperture, also known as the acceptance area.

To accurately measure matrix displays, the LMD should be configured to a circular or rectangular field of view encompassing over 500 pixels under standard observation conditions, with a total angular detection aperture of less than 2° This setup is ideally achieved at a measuring distance of 50 cm from the center of the display area, utilizing a detector acceptance area diameter of 4 cm For low-resolution matrix displays, a minimum of 9 pixels in the field of view is acceptable When measuring segment displays, the field of view must focus solely on a single segment, excluding its surroundings.

Effects of receiver inclination

When using an adjustable LMD for measuring variations based on viewing direction, it's important to recognize that the LMD perceives different sections of the DUT at various angles Initially, the measuring spot appears circular when viewed from a normal angle (θ = 0°), but as the LMD is tilted away from this position (θ > 0°), the spot transforms into an elliptical shape Notably, the short axis of the ellipse remains constant in the horizontal plane of inclination.

1 Numbers in brackets refer to the Bibliography

2 The official definition of pixel is used which may or may not include a multitude of constituent subpixels / dots

Figure 2 – Shape of measuring spot on DUT for two angles of LMD inclination

Two effects have to be considered when the LMD is adjustable The increasing size of the measuring spot with angle of inclination shall not include:

• unwanted parts of the DUT (e.g non-active parts of a display with segment-layout); or

• parts illuminated in a different way

Both size and location of the measurement field have to be selected that these conditions are fulfilled and they have to be specified accordingly.

Standard locations of measurement field

Matrix displays

NOTE Height (V) and width (H) of each rectangle are 20 % of display height and width respectively

Figure 3 – Standard measurement positions are at the centres of all rectangles p 0 - p 24

Luminance, spectral distribution and/or tristimulus measurements may be taken at several specified positions on the DUT surface To this end, the front view of the display is divided

The IEC 1103/12 standard divides the area into 25 identical imaginary rectangles, as illustrated in Figure 3 Measurements should be taken at the center of each rectangle, ensuring that the measuring spots on the display do not overlap It is essential to position the measuring spots within 7% of the specified horizontal (H) and vertical (V) directions.

(where H and V denote the dimensions of the active display area in the x and y direction respectively)

While scanning the position of the measuring spot over the surface of the DUT, the viewing direction (defined by angles θ and φ) shall not change

Any deviation from the above-described standard positions shall be added to the detail specification.

Segment displays

Standard measurement positions are the same as those prescribed for matrix displays above

For segment displays, measurements must be taken at the center of a segment, ideally positioned near the center of the designated rectangle When measurements are requested for position $ p_i $ (where $ i = 0 $ to $ 24 $), the detector should be positioned at the geometrical center of the segment that is closest to the center of box $ p_i $.

Any deviation from the above-described standard positions shall be added to the detail specification.

Standard DUT operating conditions

General

The optical properties of LCDs are significantly influenced by the viewing direction, making it essential to maintain precise mechanical control and specification of this direction when determining various parameters Additionally, it is crucial to keep the distance between the light measuring device and the measurement spot on the device under test (DUT) constant across all viewing angles.

The module under test must be physically prepared and thermostatically controlled to ensure stable operation of liquid crystal display devices for a duration of less than one hour If the control period is under one hour, the stable temperature must be verified and reported, particularly at the center of the device under test (DUT) Testing should occur under nominal conditions of input voltage and current, with any deviations from standard operating conditions documented in the detailed specifications.

Standard ambient conditions

Measurements shall be carried out, after sufficient warm-up time for illumination sources and

DUTs (see 6.12) under the standard environmental conditions, at a temperature of

25 °C ± 3 °C, at a relative humidity of 25 % to 85 %, and at an atmospheric pressure of

86 kPa to 106 kPa When different environmental conditions are used, they shall be noted in the detail specification.

Standard measuring process

The standard measuring process involves several key steps: First, prepare the measurement equipment, the Device Under Test (DUT), and the ambient conditions to ensure compliance with specified standard values and stabilities Any deviations from standard conditions must be documented in the detailed specification, including the actual values used Second, with careful attention typical of an optical metrology laboratory, measure the sample luminance in terms of luminance, spectral radiance distribution, or tri-stimulus values under the defined illumination and electrical driving conditions Lastly, measure the luminance of the applicable reference standards under the same specified conditions used for the DUT measurements.

If an external light source is used, measure the following parameters of the light source in the plane of the DUT At p 0 , measure and specify:

• temporal stability of the luminance L(t), and

• luminance distribution with viewing direction L(θ , φ)

When measuring lateral variations (see 6.7), measure the spectrum of emission, luminance and luminance distribution with viewing direction also at the other relevant positions p 1 -p 24

To achieve the target data, such as luminance and chromaticity, the measurements from the Device Under Test (DUT) must be appropriately correlated with those from the reference standard The calculation method should adhere to established guidelines, such as those provided by the CIE, and must be clearly outlined in the detailed specification.

Detailed drawing and photos of the actually used arrangement are useful to define the measurement geometry

Luminance – photometric

Purpose

This method is utilized to measure the luminance and lateral uniformity within the active area of LCD modules equipped with a built-in backlight system In contrast, for LCD modules that lack a backlight system, the measurement of transmittance must be performed.

Measurement equipment

An LMD, along with a driving power supply and a signal generator, is essential for operating liquid crystal display devices and temperature control systems, such as climatic chambers Additionally, a dual-axis positioning device may be necessary for accurate lateral uniformity measurements.

Measurement method

Measurements are conducted in a dark room under standard conditions, focusing on the designated viewing angles First, position the Device Under Test (DUT) and adjust the Light Measurement Device (LMD) to the specified angles, θ and φ Next, provide input signals to the DUT to achieve a full white condition across the entire active screen area, and measure the luminance $L_{W,i}(\theta, \phi)$ at position $p_i$, where $p_0$ is the center of the active area or the center of a segment for segmented displays Finally, supply input signals to the DUT to reach a full black condition and measure the luminance $L_{K,i}(\theta, \phi)$ at the same position $p_i$.

Definitions and evaluations

Y is the Y-tristimulus value in the CIE 1931 colorimetric system (see CIE 15);

L is the symbol for luminance, and in this particular case equal to the Y-tristimulus value;

L e (λ) is the measured radiant power per unit solid angle per unit area in the wavelength interval ∆(λ);

V(λ) is the luminous efficiency function for photopic vision in the wavelength interval ∆ ( λ );

∆ ( λ ) is the wavelength interval over which the summation takes place

Maximum luminance, denoted as \$L_{max,i}(\theta, \phi)\$, represents the peak luminance value observed in a specific viewing direction defined by the inclination angle \$\theta\$ and the rotation angle \$\phi\$ It is specifically defined when both angles are set to 0, with the Device Under Test (DUT) being evaluated at position \$p_0\$.

Minimum luminance, denoted as \$L_{min,i}(\theta, \phi)\$, represents the lowest luminance value measured in a specified viewing direction defined by the inclination angle \$\theta\$ and the rotation angle \$\phi\$ It is specifically defined for the scenario where both angles are set to 0, with the Device Under Test (DUT) being evaluated at position \$p_0\$.

Contrast ratio

Purpose

To determine the contrast ratio of the DUT.

An LMD serves as a driving power supply and signal generator for LCD devices, and it can include a temperature control device for the device under test (DUT), such as a climatic chamber Additionally, a dual-axis positioning device may be necessary for conducting lateral uniformity measurements.

Measurement method

To ensure the Device Under Test (DUT) operates under the specified driving conditions, supply the appropriate signals Measure the DUT at position p0, which is the center of the display's active area, in the WHITE state (100% input data-signal or video level) to obtain L max.

BLACK state (0 % input data-signal or video level) to obtain L min (see 6.1.4.3).

The contrast ratio CR is defined in the condition of CR≥ 1 as: min max

6.2.4.2 Definition of plain field contrast ratio ( CR PF )

To determine the maximum luminance (L max), a test pattern displaying WHITE (100% input data-signal) is used across the entire active screen area Conversely, the minimum luminance (L min) is assessed with a test pattern that shows BLACK (0% input data-signal) on the full active screen area.

The plain-field contrast ratio CR PF is defined as:

6.2.4.3 Window contrast ratio (high resolution display)

The module operates using a test pattern that produces a WHITE signal (100% input data-signal or video level) across 25 rectangles, with the exception of rectangle p0, which displays BLACK (0% input data-signal or video level) Consequently, this configuration results in a black window occupying 4% of the display area.

(Alternatively, it is allowed to shrink the window homogeneously to an area of 2,78 %, i.e a window of 1/6 × 1/6 of the total display area)

The background can be set to BLACK while the rectangle is driven WHITE, resulting in the "dark-image contrast ratio on a light field" (CR dol) and the "light-image contrast ratio on a dark field" (CR lod) The luminance of rectangles p 3 and p 7 is measured, with L max,i representing the luminance on WHITE at position i and L min,i indicating the luminance on BLACK at position i This leads to the definition of the contrast ratio as min,0 max,7 max,3 dol L.

CR min,7 min,3 max,0 lod 2

Crosstalk can negatively impact the values of CR lod and CR dol, but it does not influence the determination of CR PF Additionally, stray light may be produced by the Device Under Test (DUT) when measuring the window contrast ratio, necessitating careful evaluation and control.

Specified conditions

The records of the measurement shall be made to describe deviations from the standard measurement conditions and include the following information:

– Driving signals (waveforms, voltage and frequency).

Chromaticity and reproduction of colour

Purpose

This method is utilized for measuring the chromaticity or color gamut of liquid crystal display devices, specifically for matrix-type displays equipped with a built-in backlight system.

An LMD (spectrophotometer or a colorimeter), a driving power supply and a driving signal generator for liquid crystal display devices are used for these measurements.

Measurement method: photoelectric tristimulus colorimetry

Tristimulus colorimeters are specialized filter radiometers designed to replicate the CIE 1931 color-matching functions, x(λ), y(λ), and z(λ), across different wavelengths The outputs from these radiometers correspond to the X, Y, and Z tristimulus values, enabling the calculation of various color descriptors.

Weight factors for the illuminant and filter photometer; S(λ ) x(λ ), S(λ ) y(λ ), S(λ ) z(λ) correspond to values given in ISO 11664-2 (CIE S 014-2/E:2006)

For minimising the error, the LMD should be calibrated against a known lightsource (usually

CIE Illuminant A) before measuring the DUT

Measurements are conducted at position p0, which is the center of the display The maximum values of the primary color input signals—red (R), green (G), and blue (B)—are supplied simultaneously to the device Following this, the contrast ratio is maximized at these input values Finally, the device under test (DUT) is measured at position p0 to obtain the tristimulus values.

To obtain tristimulus values under full BLACK conditions, supply the signals to the device and measure the position $ p_0 $ to get $ X_K, Y_K, Z_K $ If necessary, provide signals for any intermediate grey states and measure $ p_0 $ for $ n $ intermediate states to obtain tristimulus values $ X_{g1} \ldots X_{gn}, Y_{g1} \ldots Y_{gn}, Z_{g1} \ldots Z_{gn} $ Next, supply the maximum R-data input signal while setting the complementary primaries to minimum or zero, and measure the red color tristimulus values $ X_R, Y_R, Z_R $ Similarly, measure the green and blue color tristimulus values $ X_G, Y_G, Z_G $ and $ X_B, Y_B, Z_B $.

Measurement method spectrophotometric colorimetry

Spectrophotometry method measures spectral radiance using a spectrophotometer and determines tristimulus values using a spectrophotometer

The spectrophotometer for spectrophotometry is classified into the first-class or second-class spectrophotometer according to CIE 15

Position the DUT, and directly record a value of S(λ ).

In the CIE 1931 colorimetric system (see CIE 15), the following tristimulus values are defined: λ λ λ ∆

S(λ ) is the measured spectral radiance distribution of the DUT in the wavelength interval ∆ ( λ); x(λ ), y(λ ) and z(λ ) are the colour matching functions for the CIE 1931 standard colorimetric observer (see CIE 15);

∆(λ) is the wavelength interval over which the summation takes place

For tristimulus values calculation, the suitable weight factor; S(λ ) from ISO 11664-2

(CIE S 014-2/E:2006) is to be used according to the illuminant, observer and wavelength interval If not specified, illuminant D65 is to be used

The chromaticity coordinates of the full WHITE; x W , y W , the chromaticity coordinates of the full

BLACK; x K , y K , and the chromaticity coordinates of the intermediate states (x gn ,y gn ) are defined as:

= + (11) gn gn gn gn X Y gn Z x X

= + , gn gn gn gn X Y gn Z

6.3.5.3 Chromaticity of primaries and colour reproduction

The chromaticity coordinates of the primaries R (x r ,y r ), G (x g ,y g ) and B (x b ,y b ) are defined as:

The colour gamut is represented by the triangle in the x-y chromaticity diagram formed by the above measured colour points (x r ,y r ), (x g ,y g ) and (x b ,y b ) as corner points

NOTE The colour gamut of u’ and v’ in the CIE 1976 chromaticity diagram (see CIE 15) is calculated from the measured x - y gamut’s by using the following formula: y + x -

• driving signals (waveforms, voltage and frequency);

• grey-level per measured colour primary.

Viewing angle range

Purpose

The determination of the angles (θ, φ) that yield maximum contrast, known as the peak viewing direction, is essential Additionally, it is important to identify the range of viewing angles, both horizontally and vertically, where the specified conditions are satisfied.

CR va = 2, 3, 4, 5, or 10) The design viewing-direction is the preferred viewing-direction as specified by the manufacturer (see blank detail specification).

An LMD, which includes a spectrophotometer, luminance meter, or filter photometer, is utilized alongside a driving power supply and a signal generator Additionally, goniometer stages, both horizontal and vertical, are employed for precise measurements of displays or detectors.

Contrast and luminance based viewing angle range

The measurements are performed in the dark room under standard measuring conditions and design viewing direction

Determine the total range of viewing directions to be measured for determination of the viewing angle range Care should be taken that the correct relation between light source and

Measure luminance of the “WHITE” state, L max (θ , φ), and “BLACK” state, L min (θ , φ ), in the normal direction as well as on all coordinates (θ , φ) selected, according to 6.1.4.2, and 6.1.4.3

NOTE If the optimal direction is known, an inclination scan in azimuth direction φ = 0°, 90°, 180°, 270° will suffice

If the optimal direction is unknown, a full scan over a wide range of inclinations and azimuth directions ( θ , φ ) may be necessary

To calculate the contrast ratio, measure the luminance at each position as specified in section 6.2.4.2 Identify the range—horizontal, vertical, or both—where the evaluated parameter, such as luminance or contrast ratio, surpasses the selected limit value $ x $ The threshold angle is denoted as $ \theta(\phi[x]) $.

The peak viewing direction (θ , φ ) peak is defined by the direction for which maximum contrast ratio CR PF,max (θ , φ ) is found

The horizontal viewing angle range (VAR_H) and the vertical viewing angle range (VAR_V) are now defined by:

• Horizontal viewing angle range (luminance = x): VAR_H [L: x] = θ(0,[ x]) + θ(180,[ x]);

• Vertical viewing angle range (luminance = x): VAR_V [L: x] = θ(90,[ x]) + θ(270,[ x]);

• Horizontal viewing angle range (contrast ratio=CR): VAR_H [CR:CR] = θ(0,[ x]) + θ(180,[ x]);

• Vertical viewing angle range (contrast ratio=CR): VAR_V [CR:CR] = θ(90,[ x]) + θ(270,[ x]) e.g.:

• The horizontal viewing angle range where luminance is 10 % of its maximum value is presented by VAR_H [L: 10 %];

• The vertical viewing angle range where luminance is 10 % of its maximum value is presented by VAR_V [L: 10 %];

• The horizontal viewing angle range of contrast ratio of 3 is presented by VAR_H [CR: 3];

• The vertical viewing angle range of contrast ratio of 3 is presented by VAR_V [CR: 3]

Records of the measurement shall be made to describe deviations from the standard measurement conditions and further include the following information:

• selected standard measuring system and its related conditions;

• conditions for viewing angle ranges (luminance, contrast ratio);

• luminance and contrast ratio reference values.

Viewing angle range without grey-level inversion

Measurements are conducted in a dark room under standard conditions The image signal at position $ p_0 $ must include $ N $ distinct grey levels, evenly distributed between the "black" and "white" field levels, with $ N $ being at least 8.

For each grey-level (g), adjust the photometer to the 12 o’clock (θ 12), 6 o’clock (θ 6), 3 o’clock (θ 3), and 9 o’clock (θ 9) positions of the Device Under Test (DUT) Measure the luminance as specified in section 6.1 Next, identify the angular values (θ d) for each direction (d = 12, 6, 3, and 9) where the luminance remains consistent between grey-scale levels g and g+1, for g ranging from 0 to N-1.

Lum inanc e ( ar b uni ts )

Figure 4 – Example of grey-scale inversion

The horizontal and vertical viewing angles without grey-level inversion are defined as:

Horizontal viewing angle without grey-level inversion: θ GSI,H = θ 3 + θ 9 (18)

Vertical viewing angle without grey-level inversion: θ GSI,V = θ 6 + θ 12 (19)

Chromaticity based viewing angle range

Chromaticity can be assessed in relation to viewing direction using the same approach as viewing angle range measurement Instead of focusing on luminance and contrast ratio, chromaticity serves as a key parameter to define the range of chromaticity variation within specific limits Typically, the reference chromaticity coordinates are measured in the perpendicular viewing direction (x₀, y₀), while the color variation is subsequently calculated.

∆u’v’ For the definition and evaluation, see 6.7.5.2

Records of the measurement shall be made to describe deviations from the standard measurement conditions and include the following information:

• selected standard measuring system and its related conditions;

• conditions for viewing angle ranges (luminance, contrast ratio);

• colour primary measured, if applicable.

Visual quality-based viewing angle range

To be implemented in a later revision of this standard

Electro-optical transfer function – photometric

Purpose

The purpose of this measurement procedure is to obtain the relation between the electrical driving conditions of the DUT and the resulting optical response under specified conditions

Depending on the nature of the DUT the driving conditions may be specified by analogue voltage levels (video levels), or by digital input levels (e.g digital R, G, B values).

The DUT shall be placed in the measurement arrangement and it shall be assured that all required conditions are fulfilled

Before initiating the measurement process, it is essential to power on all illumination sources in the selected arrangement and allow them to stabilize, as outlined in section 5.5.2, to ensure the required stability is achieved.

The DUT has to be powered on and allowed to stabilize in order to reach the required stability

(see 5.5.2.1) before the measurement process is started.

Measurement method

The initial electrical driving conditions, including analogue input voltages or digital input signals, must be applied to the Device Under Test (DUT) Following this, a waiting period is necessary to ensure proper idle time for the device.

To achieve a stable optical state in DUT, it is essential to ensure that the idle-time is sufficiently long, as detailed in Annex C Once this condition is met, key optical quantities such as luminance, spectral radiance distribution, or tri-stimulus values should be measured Subsequently, a new set of driving signals is applied, and the measurement procedure is repeated, as outlined in Annex A.

The measurement procedure involves several key steps: first, a driving signal is applied to the entire active screen area Next, the optical output is allowed to stabilize before measuring luminance, spectral radiance distribution, or tri-stimulus values Finally, the process is repeated from the beginning.

The immediate result of the measurement procedure is an array of luminance values L-i (DUT) obtained from the LMD, as a function of the electrical driving condition (analogue or digital input)

Evaluation and representation

The resulting array of luminance values and driving voltages can be listed or graphically represented in a diagram with e.g Cartesian coordinates

From the array of luminance values obtained as a function of the electrical state of driving, a variety of integral characteristics can be evaluated according to the respective requirements.

Electro-optical transfer function – colorimetric

Purpose

This measurement procedure aims to establish the relationship between the electrical driving conditions of the Device Under Test (DUT) and the resulting optical response's chromaticity under defined conditions The driving conditions may vary based on the DUT's characteristics, being specified either by analog voltage levels, such as video levels, or by digital input levels, like digital R.

Set-up

The DUT shall be placed in the measurement arrangement and it shall be assured that all required conditions are fulfilled

Before initiating the measurement process, it is essential to power on all illumination sources in the selected arrangement and allow them to stabilize, as outlined in section 5.5.2, to ensure the required stability is achieved.

The DUT has to be powered on to be powered on and allowed to stabilize in order to reach the required stability (see 5.5.2.1) before the measurement process is started.

Measurement method

The initial electrical driving conditions, including analogue input voltages or digital input signals, must be applied to the Device Under Test (DUT) Following this, a waiting period is necessary to ensure proper idle time for the DUT.

To achieve a stable optical state in a DUT, it is essential to ensure that the idle-time is sufficiently long, as detailed in Annex C Once this condition is met, the relevant optical quantities, such as spectral radiance distribution or tri-stimulus values, must be accurately measured Following this, a new set of driving signals is applied, and the measurement procedure is repeated.

The measurement procedure involves several key steps: first, a driving signal is applied to the entire active area; next, the optical response is allowed to stabilize; then, the spectral radiance distribution or tri-stimulus values are measured; finally, the process repeats from the beginning.

The measurement procedure yields an array of spectral radiance distributions or tri-stimulus values, denoted as S(λ) i or X, Y, Z, which are derived from the light measurement device based on the electrical driving conditions, whether analogue or digital input.

The spectral radiance distribution S(λ) represents a series of values that illustrate how spectral radiance changes with light wavelength According to the CIE 1931 2° colorimetric standard observer, the tri-stimulus values consist of three distinct values, denoted as X.

, Y i (proportional to the luminance) and Z (see CIE 15)

Spectral radiance distribution stimulus values Electrical driving

The spectral radiance $ S_\lambda $ and the tri-stimulus values $ X_i $, $ Y_i $, and $ Z_i $ can be assessed to derive various colorimetric characteristics as defined by the CIE, including chromaticity coordinates, saturation, and hue.

These values can be listed or graphically represented in various chromaticity diagrams of

CIE 15 (CIE 1931, CIE 1976 UCS, etc.)

From the array of luminance values obtained as a function of the electrical state of driving, a variety of integral characteristics can be evaluated according to the respective requirements.

Lateral variations (photometric, colorimetric)

Purpose

The purpose of this measurement is to determine the homogeneity of the luminance and/or colour of the DUT.

For accurate measurements of LCD devices, a luminance meter (LMD) is utilized alongside a driving power supply and a signal generator Additionally, a positioning device is essential to ensure the correct measurement geometry for all points on the device under test (DUT).

Uniformity of luminance

To achieve optimal performance, the plain field contrast ratio (CR PF) is maximized Subsequently, the device under test (DUT) is supplied with a 100% input data signal, representing the maximum luminance state, which corresponds to a full white signal.

Finally, measure the maximum luminance (L max,d ) at the specified positions (d) in the active area The measurement is done on either five (positions p 0 , p 11 , p 15 , p 19 , and p 23 ) or nine

(positions p 0 , p 9 , p 11 , p 13 , p 15 , p 17 , p 19 , p 21 , and p 23 ) points, with the LMD perpendicular to the DUT surface

Determine the average of luminance of the full WHITE; L W(av) as per the following calculation:

W( av) (20) where N is the number of measurement positions, d is each point number

The luminance long-range non-uniformity (LNU) is then calculated by from the individual luminance L max,d and the average luminance L W(av) according to:

LNU W = 0 indicates a perfectly uniform display for the selected number of measurement positions.

Uniformity of white

The chromaticity measurement is done on either five (positions p 0 , p 11 , p 15 , p 19 and p 23 ) or nine (positions p 0 , p 9 , p 11 , p 13 , p 15 , p 17 , p 19 , p 21 and p 23 ) points (see Figure 3), with the display driven to full-frame white (highest grey-level)

The chromaticity corresponding to the measurement at position i is defined by the colour coordinates x i and y i as:

Deviations from the chromaticity at position i and from the chromaticity at the display centre are defined as colour differences as defined in CIE 1976 UCS system (see CIE 15): w(0) w w ' '

Uniformity of chromaticity

Measurements are conducted at the central position (p 0) of the display The corresponding color input signals (c) are supplied to all primary inputs: Red (R), Green (G), and Blue (B).

(blue) to the device Measure the tristimulus values; X c (i), Y c (i), Z c (i), respectively The measurement is done on either five positions (p 0 , p 11 , p 15 , p 19 , and p 23 ) or nine positions (p 0 , p 9 , p 11 , p 13 , p 15 , p 17 , p 19 , p 21 , and p 23 )

The chromaticity corresponding to the measurement at position (i) is defined by the colour coordinates x c(i) , y c(i) , as:

Deviations from the chromaticity at position (i) from the chromaticity at the display centre are defined as colour differences in an “approximately uniform colour space”, e.g as defined in

CIE 1976 UCS system (see CIE 15)

Uniformity of primary colours

Measurements are conducted at position p0, which is the center of the display First, provide the maximum values of the color input signals for all primary colors—red (R), green (G), and blue (B)—simultaneously to the device Next, optimize the contrast ratio at this maximum input level Finally, supply the maximum input signals for R, G, and B individually, while setting the data input for the complementary primaries to minimum or zero, and measure the resulting R, G, and B values.

B colour tristimulus values; X r(i) , Y r(i) , Z r(i) , X g(i) , Y g(i) , Z g(i) , and X b(i) , Y b(i) , Z b(i) respectively

The measurement is done on either five positions (p 0 , p 11 , p 15 , p 19 , and p 23 ) or nine positions

The chromaticity corresponding to the measurement at position i is defined by the colour coordinates x r( i ) , y r( i ) , x g( i ) , y g( i ) , x b( i ) and y b( i ) as:

Deviations from the chromaticity at position i from the chromaticity at the display centre are defined as colour differences in an “approximately uniform colour space”, e.g as defined in

CIE 1976 UCS system (see CIE 15)

Cross-talk

This method is applied to the measurements of the pattern dependent cross-talk level in the display device

A driving power supply, a driving signal generator and a luminance meter for LCD devices are used for these measurements

The DUT is initially driven with a full-frame grey video level to achieve a luminance value near 50% Luminance measurements are taken at positions p9, p13, p17, and p21 while viewing at a normal direction (0°), with the measured luminance at each location denoted as L ref [i].

The video information within a rectangle defined by the centers of positions p2, p4, p6, and p8, covering 40% of the display's width and height, is altered to full black The luminance at positions p9, p13, p17, and p21 is then re-measured and recorded as L_bl[i] Subsequently, the video information in the same rectangle is changed to full white, and the luminance at the specified positions is re-measured, now referred to as L_wh[i].

The horizontal white cross-talk HXT wh is defined as:

(%) ref ref wh ref ref wh wh

 ∨ × (32) and the horizontal black cross-talk HXT bl as:

(%) ref ref bl ref ref bl bl

The (total) horizontal cross-talk HXT is now defined as:

In the same manner, the vertical white cross-talk VXT wh is defined as:

(%) ref ref wh ref ref wh wh

 ∨ × (35) the vertical black cross-talk VXT bl is defined as:

(%) ref ref bl ref ref bl bl

 ∨ × (36) and the (total) vertical cross-talk VXT is defined as:

) ( max VXT bl VXT wh

6.7.7.4 Black and white (two-level) matrix displays

Measurements are performed in the dark room under standard measuring conditions

The DUT is initially activated with the ON signal, and luminance is measured at positions p 9, p 13, p 17, and p 21 under a normal viewing direction of 0 degrees, referred to as L ONref [i] Subsequently, the drive level within a rectangle defined by the centers of positions p 2, p 4, p 6, and p 8 is switched to the OFF signal, and the luminance at the same locations is re-measured, denoted as L OFF [i].

The OFF-of-ON cross-talk XT OFF/ON is defined as:

The DUT is initially driven with the OFF signal, and luminance is measured at positions p 9, p 13, p 17, and p 21 under a normal viewing direction of 0 degrees, referred to as L OFFref [i] Subsequently, the drive signal within a rectangle defined by the centers of positions p 2, p 4, p 6, and p 8—covering 40% of the display's width and height—is switched to the ON signal The luminance at the same locations is then re-measured, resulting in values denoted as L ON [i].

The ON-of-OFF cross-talk XT ON/OFF is defined as:

The measurement results can be significantly influenced by the resolution of the LMD To enhance measurement resolution, several options are available.

• change the viewing-direction in order to make the crosstalk more visible; or

• change to operating (battery) voltage in order to make the crosstalk more visible

Both modifications shall be explicitly specified in the results.

Mura

To be implemented in a later revision of this standard.

Image sticking

To be implemented in a later revision of this standard.

Reflectance from the active area surface

Purpose

Reflections from ambient light sources on display surfaces can cause discomfort and disability glare, negatively impacting the visual performance of LCDs This standard focuses on non-Lambertian reflections, as LCDs typically lack Lambertian diffuse reflection components The scattering from a matte surface is characterized by two appropriate specular reflectance measurements using different light source apertures.

This technique measures the specular surface reflectance of the display device's active area, capturing the effects of external input light.

Light source with adjustable aperture (1° and 15°), an LMD and positioning mechanism are required.

Measurement method

Measurements are conducted in a dark room under standardized conditions, focusing on the center of the display's active area The light source, device under test (DUT), and luminance meter are arranged to be coplanar, with an inclination of approximately 15° relative to the normal of the DUT surface, as illustrated in Figure 5.

• The light source(s) shall provide a uniform luminance across the exit aperture The deviation of luminance shall be less than 5 %

• The light source luminance shall be stable over time No long-term or short-term luminance fluctuations shall exceed 1 %

• In order to assure a high signal-to-noise ratio for the luminance meter, the luminance of the light source shall be sufficiently high (e.g 5 k cd/m 2 and more)

• The spectral distribution of the light source shall be specified It is recommended to use light sources with a correlated colour temperature as close to illuminant D65 as possible

The aperture angles of the light source are determined from the center of the measurement spot on the Device Under Test (DUT) It is essential that no other light sources interfere with the measurement process.

The DUT should not be illuminated by a backlight unit, but specular reflectance can be assessed in both the OFF-state and the "dark" or "bright" states The luminance meter must be directed at the exit port of the light source If the DUT has a scattering surface, such as an anti-glare layer, a microscope cover glass or clear plastic adhesive tape should be used for mechanical adjustment and focusing The measurement field of the luminance meter must not exceed 0.5° for a 1° source aperture and 1° for a 15° source aperture, with the measuring spot centered within the exit aperture of the source.

In order to obtain an indication for the non-specular components in the reflectance, the reflectance of the DUT is measured under two different illumination conditions θ b θ out θ in θ a

Figure 5 – Example of standard set-up for specular reflection measurements

The power and driving signal are not supplied to the device The angle of observation by the luminance meter to the display surface shall be θ out = θ in (40)

The total aperture angle of the illuminating light should be θ a = 1° for measurement of R 1 and θ a = 15° formeasurement of R 15 The total aperture angle of the luminance meter shall be

The angle $ \theta $ should be maintained within the range of 0.1° to 0.5° and kept constant throughout both measurements The distance from the surface of the Device Under Test (DUT) to the light source is denoted as $ l_1 $, typically set at 50 cm, while the distance from the DUT surface to the luminance meter is referred to as $ l_2 $.

Measure the luminance from the source L R [i] after reflection from the DUT at the centre position (i = 0) The detector shall be focused at the lamp (rather than the display surface)

Calibrate the light source by positioning the luminance meter directly in front of the light source at distance l 1 + l 2 and thus measure L 01 and L 15 for both apertures of the light source,

NOTE Because of the dependence on the orientation of liquid crystal molecules, the reflectance values can be dependent on the LCD driving state (off, black or white).

Definitions and evaluation

The reflectance factor from the centre position R [i=0] is given by Equations 41 and 42:

With increasing scattering the difference between R 1 and R 15 also increases The perfect flat non-scattering surface does not exhibit any differences between R 1 and R 15.

• Angles for the incident light (θ in ) and the reflected light for the luminance meter (θ out );

• aperture angles of the light source (θ a ) and the luminance meter;

• type of light source (spectrum and luminance);

• driving-state of the display device

Special care should be used when a 1º source geometry is used due to a higher probability of error.

Spectral transmittance factor

Purpose

This method aims to measure the spectral transmittance of a liquid crystal cell independently from the light source By utilizing known or assumed characteristics of the backlight system, it is possible to derive virtual luminance values, which can then be used to calculate various optical parameters, such as the contrast ratio.

Spectrophotometry method measures spectral radiance using a spectrophotometer and determines tristimulus values using a spectrophotometer

The spectrophotometer for spectrophotometry is classified into the first-class or second-class spectrophotometer according to CIE 15.

Definitions and evaluation

The spectral transmittance factor, T(λ), of the device under test (DUT) is calculated by comparing it to the light source The measurement procedure involves first measuring the light source to obtain a value of Τ w ’(λ) Next, the DUT is placed in the light path to record a value of Τ’(λ) Finally, the spectral transmittance factor T(λ) of the DUT is determined using a specific formula.

The spectral transmittance factor of the device under test (DUT) is denoted as T(λ), while Τ’(λ) represents the radiance value for each wavelength of the DUT Additionally, Τ w ’(λ) indicates the radiance value for each wavelength of the light source The tristimulus values, X, Y, and Z, are calculated based on these parameters.

S(λ ) is the relative spectral radiant power distribution of the light source; x(λ), y(λ), z(λ) are the colour matching functions for CIE 1931 standard observer (see CIE

T(λ ) is the spectral transmittance factor of the DUT;

∆ ( λ ) is the wavelength interval for tristimulus values calculation

For tristimulus values calculation, the suitable weight factor, S(λ), from ISO 11664-2 (CIE S

014-2/E:2006) is to be used according to the illuminant, observer and wavelength interval If not specified, an illuminant as close to D65 as possible shall be used.

Temporal variations

Response time

The time required to transition from light to dark (or dark to light) is influenced by the applied driving voltage These light and dark states can also represent any two grey levels on a grey scale-capable display, allowing for the measurement of response times between any selected grey levels.

In LCD technology, the term "turn-on" refers to the response of the display when the driving voltage increases, while "turn-off" describes the relaxation that occurs when the voltage decreases This definition is simple for segment and low-resolution LCDs, but it becomes more complex for high-resolution matrix LCD screens due to the intricate data processing involved.

An LMD with sufficient frequency response and sufficiently fast response time, a power supply, a driving signal generator, a trigger signal generator and a recorder

Figure 6 – Example of equipment for measurement of temporal variations

The measurements are performed in the dark room under standard measuring conditions

Use the measurement circuit system as shown in Figure 6, and measure response curves For an example, see Figure 7

3 As a consequence ISO 13406-2 (now withdrawn – see ISO 9241-307) uses the term "image formation time"

The turn-on and turn-off processes involve distinguishing between positive and negative contrast polarity In the case of positive contrast polarity, the turn-on process switches from "light" to "dark," which is essential for generating an image against a bright background.

The electrical signal from the detector, located at position $ p_0 $ in the design-viewing direction, is transmitted to the recorder The display operates using an invertible plain field signal generated by a signal generator When inverted, the signal transitions directly from the start level to the end level, omitting any intermediate levels on the display The inversion frequency is kept low to ensure that the display achieves optical equilibrium in both states.

A trigger signal is activated at position p 0 when the video is inverted If the timing of this trigger signal differs, such as occurring at the start of the field, adjustments must be made to account for the scanning time \$t_s\$ required for the video-signal inversion to reach position p 0 The luminance meter is used to measure the optical response, and any ripples in the detected signal caused by irrelevant factors, like display frame frequency, must be removed The luminance is set to 100% in light mode and adjusted accordingly in dark mode.

For high-resolution displays exceeding 320 × 240 pixels, it is crucial to ensure that the measured response times are not significantly affected by the time required for the display to scan the measuring spot The display frame time, denoted as T = 1/f_{FRM} (where f_{FRM} is the frame frequency), is influenced by the number of rows (N_{row}) and the vertical pixel pitch (V_{pitch}) Consequently, the display height (H) in the scanning direction is calculated as H = N_{row} × V_{pitch} Additionally, the diameter of the measuring spot in the same direction is represented by S, which must be considered when evaluating the measured response times (t).

The times needed for the luminance at position p 0 to change from 0 % → 90 % (t 1 ) and

The measurements indicate a transition from 100% to 10% luminance, as illustrated in Figure 7 At the same position, the times required for luminance to shift from 10% to 90% (denoted as \$\tau_1\$) and from 90% to 10% (denoted as \$\tau_2\$) are recorded We define the turn-on time (\$t_{on}\$) and turn-off time (\$t_{off}\$) for displays that are normally white and normally black.

DUT according to: t on = t 2 (t 1 ) (49) and t off = t 1 (t 2 ) (50) and the rise-time (t r ) and fall time (t f ) according to: t r = τ 2 (τ 1 ) (51) and t f = τ 1 (τ 2 ) (52)

Dynamic response times, often referred to as switching times, include both on- and off-times as well as rise- and fall-times These terms are general and not strictly defined The distinction between turn-on/turn-off times and rise/fall times is known as delay time.

Figure 7 – Relationship between driving signal and optical response times

• measurement equipment and detector specification;

• colour and / or grey level displayed;

When utilizing the terms "switching-time" or "(dynamic) response time," it is essential to provide a detailed explanation in the specifications Any deviations from the prescribed nomenclature should be clearly stated when alternative names for these times are used.

Flicker / frame response (multiplexed displays)

This method assesses the temporal variation of display luminance in multiplexed and matrix displays, often referred to as "flicker." However, flicker specifically pertains to the perceptual effects of these variations, which are influenced by factors such as luminance, color, and observation direction Section 6.10.2.4 addresses the determination of temporal fluctuations by considering the frequency response of the human visual system, while section 6.10.3 employs a metric to predict flicker visibility based on measured temporal luminance variations.

More relevant information about the technical and perceptive issues of display flicker can be found in [5], [6] and [7]

An LMD, or fast luminance-sensitive photodiode, requires a power supply and a driving signal generator It is essential that the -3dB frequency of the LMD is at least ten times greater than the display's frame frequency.

First, the contrast ratio is adjusted to the maximum value Next, the luminance is adjusted to

To measure luminance effectively, first select a grey-level or video input signal at 50% of its maximum Then, use a luminance meter or luminance-sensitive photodiode to assess the luminance at the center of the active area over time To incorporate the frequency response of the human visual system, the luminance meter's signal can be processed through an integrator with visual sensitivity characteristics before recording the frequency response on a frequency analyzer Alternatively, one can account for the human visual system's frequency response by numerically multiplying the measured power spectrum with the response function provided.

For frequencies in the range of 0 Hz to 60 Hz, it is essential to determine the power present in the spectrum and identify the component with the maximum power value, denoted as $ P_{f \, \text{max}} $ An example of a power spectrum can be referenced in Figure 9 The flicker level $ F $ is calculated based on these findings.

Figure 8 – Frequency characteristics of the integrator

(response of human visual system)

Figure 9 – Example of power spectrum

An FFT analyzer should be used for evaluation.

Critical flicker frequency

From the measured temporal luminance distribution we would like to predict if flicker will be observed For this, the model already described by Farrell [6] can be successfully used [7]

The critical flicker frequency (CFF) is the minimum refresh rate required to ensure a display appears flicker-free When the refresh rate exceeds this value, the display provides a smoother visual experience.

CFF, it is predicted that the observer will not perceive flicker

The retinal illumination (\$E_{ret}\$) is influenced by the luminance entering the eye (\$L\$) and the pupil area (\$A_{pupil}\$), which is determined by the pupil diameter (\$d\$) The normalized modulation amplitude of the fundamental frequency, denoted as \$M(f)\$, is derived from the time-varying screen luminance Additionally, parameters \$m\$ and \$n\$ are dependent solely on the display size It is essential to report both the calculated CFF-value and the refresh rate used.

Records of the measurement shall be made in order to describe deviations from the standard measurement conditions (see Annex A) and shall include the following information:

• the absolute value of the luminance at which the flicker measurement was performed (i.e

50 % of the maximum value of the device)

Electrical characteristics

Purpose

This technique is utilized to measure the power consumption and current of liquid crystal display (LCD) devices, which consist of a display module along with a driving circuit and/or logic circuit.

The electrical characteristics are measured by using a driving power supply, DC voltage meter,

DC current meter and a pattern generator.

Measurement method

6.11.3.1.1 Standard power consumption measuring method

Figure 10 – Checker-flag pattern for current and power consumption measurements

Measurements are conducted under standard conditions, utilizing a checker-flag pattern signal supplied to the liquid crystal display device This is achieved through driving signals and a specialized pattern generator, ensuring that both bright and dark areas are displayed equally.

To achieve the maximum contrast ratio in the display pattern, it is essential to optimize the display signals The voltage provided to the circuits within the display device must be adjusted to the nominal values outlined in the detailed specifications.

If the module has a built-in backlight system, the power consumption of the backlight system is determined with the luminance set to the maximum specified value

Measure the currents of I 1 , I 2 , and I 3 of the drive circuits, flowing in the following circuits shown in Figure 11

All display segments of interest shall be connected in such a way that their individual currents are added in the overall driving current

The power consumption in each of the circuits is calculated by the following formulas:

• Power consumption in the logic circuit: P 1 = E 1 × I 1;

• Power consumption in the liquid crystal display driving circuit: P 2 = E 2 ×I 2;

• Total power consumption in the display device: P 0 = P 1 + P 2

When the liquid crystal display device has grey scale display capability, the measurements are carried out using the grey scales corresponding to the maximum and minimum luminance

When the standard checker flag pattern is not utilized for measurements, it is essential to specify the display pattern used, such as a color bar, grey scale pattern, or checker pattern, in the detailed specifications.

To accurately assess the total current and power consumption of a liquid crystal display device, it is essential to measure the overall voltage and current when the circuit does not separate the logic from the liquid crystal driving circuitry.

To optimize power efficiency, adjust the liquid crystal driving conditions and voltage as outlined in the detailed specifications Under these parameters, the measured individual and total power consumption will be defined as the maximum power consumption.

• liquid crystal display driving signal frequency( displayed pattern signal condition);

• conditions for maximum power consumption;

• logical states of the data inputs to the segments (segment displays only);

• backlight system when the device has only a light source, specify its driving condition;

Figure 11 – Example of measuring block diagram for current and power consumption of a liquid crystal display device

Warm-up characteristics

Purpose

This method is utilized to measure the turn-on luminance transient characteristics of transmissive liquid crystal display devices equipped with a built-in backlight system, primarily focusing on effects related to warm-up.

A luminance meter, a driving power supply and a driving signal generator for LCD devices are used for these measurements.

Measurement method

The measurement shall be performed under dark-room and standard measurement conditions unless otherwise specified

To achieve maximum transmittance of the LCD, the DUT must be supplied with all necessary voltages and input data Luminance measurements will be conducted at position p0, recording the luminance over time until fluctuations drop below 1% of the mean value This mean value should be calculated from at least 10 measurements taken over approximately 15 minutes.

The "luminance value after stabilization, L stab," refers to the mean luminance level achieved once it has reached a stable state It is essential to maintain consistent measuring conditions throughout the duration of the luminance recording.

Voltage meter Voltage meter Voltage meter

Current meter Current meter Current meter

Figure 12 – Example of warm-up characteristic

Numerical characteristics can be derived from the recorded luminance versus time values by computation of e.g t 90 (time period required for the luminance to reach 90 % of L stab )

When the time dependent luminance data are required for other positions, measure the luminance at these positions

• timing of data-acquisition (sampling frequency and integration period)

Luminance meter: devices for measuring luminance can be realized by:

• a photometer with filter adaption to V(λ)

Colorimeter: Devices for measuring colour can be realized by:

Display devices are commonly utilized in various lighting environments, including office settings and home use for personal computers, word processors, audio-visual equipment, and telephones ISO 9241-7 outlines the lighting conditions necessary for optimal use of these devices, incorporating guidelines from the National Institute for Occupational Safety and Health (NIOSH) regarding Visual Display Terminals.

Safety and Health in U.S.A.) and the Labour Ministry in Japan and the luminance of the surface of active area in the vertical direction is specified

A.3 Device without built-in backlight system

The type-D65 light source is different in colour temperature and spectrum from normally used

The characteristics of light sources, whether incandescent or fluorescent, are crucial for liquid crystal display devices Currently, there is no universally accepted standardized light source, leading to the specification of type-D65 light in this standard.

A.4 Light measurement methods and equipment

A.4.1 Apparatus for angular resolved luminance measurement

Controlling the geometric conditions of the light source, the device under test (DUT), and the light measurement device (LMD) is crucial for ensuring the significance and reproducibility of light transmission measurements Regardless of the method used for positioning, it is essential that the setup remains stable and consistent.

Measurement of the light transmitted through LCDs as a function of the direction of observation (i.e viewing-direction) can be carried out with two classes of instruments [2]:

• optical scanning instruments (conoscopic method)

Both approaches are allowed for measurement and evaluation of LCDs as described in this standard

Light measuring devices [LMDs] that can be used for the purpose of this standard comprise the following components:

• an optical system for imaging a well-defined spot of the DUT onto the detector;

• an optical system for viewing the measuring spot on the DUT (viewport);

• electronics for amplification, processing and storage of the electrical signal(s) from the detector

Aspects that have to be taken into account, measured and specified are:

• angular aperture (shall be below 5°);

• sensitivity to polarization of light;

• frequency range and integration periods

The spectral sensitivity of LMDs that can be used for the purpose of this standard are classified as follows:

• photometric (referring to radiation as evaluated according to the spectral luminous efficiency function of the human eye, V(λ) CIE 1931) (see CIE 15);

• colorimetric (according to the tristimulus values X, Y and Z according to CIE 1931) (see

• spectro-radiometric (providing spectrally resolved radiant energy data)

Field of view Angular field of view

Focus on object being measured

In addition to LMDs that calculate an average value for the measured quantity within a specific area, there exists a category of imaging techniques that enhance measurement accuracy and detail.

LMDs provide values, such as R, G, and B, for each area element on the Device Under Test (DUT) These LMDs can effectively replace traditional sequential mechanical scans of a display's surface by capturing a "snapshot" of the DUT for subsequent data evaluation.

Aspects to be considered when imaging LMDs are used:

• stray-light within LMD ( e.g lens flare, veiling glare);

• non-uniformities of sensitivity across detector area;

• cos 4 θ variation of detector illuminance;

In addition to LMDs that create an image of the measurement field on the detector, there exists another category of LMDs that directly capture the directional distribution of light emanating from the measurement field on the Device Under Test (DUT) These specialized devices are referred to as "conoscopic."

Measurements on LCDs generally have to take place under controlled, known circumstances

Temperature is a crucial parameter in testing, as operating the Device Under Test (DUT) under controlled room conditions can ensure a stable temperature However, there are instances where it becomes essential to implement thermostatic control for the display itself.

There are several methods to maintain temperature control for the Device Under Test (DUT) One reliable approach is to suspend the DUT inside a thermostatic chamber, although this can be impractical if the Load Measurement Device (LMD) also needs to be housed within the chamber Alternatively, mounting the DUT on a thermostatically controlled surface offers a more practical solution, but it may necessitate additional measures to prevent condensation when operating at temperatures below room temperature.

Measuring the electro-optical transfer function

Liquid crystal displays (LCDs) are devices that modulate light, with the transmitted light dependent on the applied RMS voltage This relationship is known as the "electro-optical transfer function."

To measure the relationship between voltage and light transmission in an LCD cell, begin at a low voltage (e.g., 0 V) and apply small voltage increments while measuring light transmission until reaching a predefined high voltage (e.g., 5 V) It is crucial to allow adequate time between voltage changes and measurements to ensure stable optical transmission For verification, repeat the measurement by starting at the high voltage and applying small decrements in voltage; both methods should yield consistent results.

Part number Part title Remarks

61747-1-1 Generic – Generic specification Amends and replaces IEC 61747-

61747-1-2 Generic – Terminology and letter symbols Amends and replaces IEC 61747-

1 (Clauses 1, 2, and 3) 61747-2 Liquid crystal display modules -

61747-2-1 Passive matrix monochrome LCD modules -

Blank detail specification Maintain IEC 61747-2-1

Blank detail specification Maintain IEC 61747-2-2

61747-3 Liquid crystal display (LCD) cells -

61747-3-1 Liquid crystal display (LCD) cells -

Blank detail specification Keep IEC 61747-3-1

61747-4 Liquid crystal display modules and cells -

Essential ratings and characteristics Keep IEC 61747-4 61747-4-1 Matrix colour LCD modules -

Essential ratings and characteristics Keep IEC 61747-4-1 61747-10-1 Environmental, endurance and mechanical test methods - Mechanical

5 Clause 1 and 2 61747-10-2 Environmental, endurance and mechanical test methods - Environmental and endurance

5 Clauses 1 and 3 61747-10-4 Environmental, endurance and mechanical test methods - Glass strength and reliability

Monochrome liquid crystal display cells (Excluding all active matrix liquid crystal display modules)

Monochrome matrix liquid crystal display modules (Excluding all active matrix liquid crystal display modules)

Active matrix colour liquid crystal display modules Replaces IEC 61747-5-2 61747-30-1 Functional measurement methods for liquid crystal display modules - Transmissive type

61747-30-2 Functional measurement methods for liquid crystal display modules - Reflective type

61747-30-3 Functional measurement methods for liquid crystal display modules - Transmissive type motion artifact

Mechanical testing guidelines for display cover glass for mobile devices

ISO 9241-7, Ergonomic requirements for office work with visual display terminals (VDTs) –

Part 7: Requirements for display with reflections (withdrawn)

[1] M E Becker, "LCD Visual Performance Characterization and Evaluation", 1999 SPIE

Flat Panel Display Technology and Display Metrology Conference, San Jose

[2] M E Becker, "Measuring LCD Optical Performance", SID 1996, San Diego, Application

[3] M E Becker, "Viewing-cone Analysis of LCDs: a Comparison of Measuring Methods",

[4] M E Becker, J Neumeier, "Measuring LCD electro-optical performance", SID 1992,

[5] Vesa Flat Panel Display Measurements Standard, Version 2.0

[6] J E Farrell, et al., “Predicting flicker thresholds for video display terminals”, Proc of the SID 28, No 4, (1987), pp 449–453

[7] L Wang, C Teunissen, Y Tu, and L Chen, “Flicker visibility in scanning-backlight displays”, Journal of the SID 16/2, (2008), pp 375-381

4 Eclairement et géométrie de l'éclairement 55

4.1 Commentaires et remarques généraux concernant la mesure des LCD transmissifs 55

4.2 Système de coordonnées de la direction d'observation 56

5 Montage et équipement de mesure standard 57

5.1 Dispositifs de mesure de la lumière (LMD) 57

5.3.2 Effets de l'inclinaison du récepteur 58

5.4 Emplacements standard du champ de mesure 59

5.5 Conditions de fonctionnement normales des DUT 60

6.3 Chromaticité et reproduction des couleurs 64

6.3.3 Méthode de mesure: colorimétrie trichromatique photo-électrique 64

6.3.4 Méthode de mesure: colorimétrie spectrophotométrique 64

6.4.3 Gamme d'angles de vision selon le contraste et la luminance 67

6.4.4 Gamme d'angles de vision sans inversion des niveaux de gris 68

6.4.5 Gamme d'angles de vision selon la chromaticité 68

6.4.6 Gamme d'angles de vision selon la qualité visuelle 69

6.5 Fonction de transfert électro-optique – photométrique 69

6.6 Fonction de transfert électro-optique – colorimétrique 70

6.7 Variations latérales (mesure photométrique, colorimétrique) 71

6.8 Facteur de réflexion provenant de la surface de la zone active 76

6.10.2 Papillotement / réponse de trame (afficheurs multiplexés) 82

Annexe A (informative) Conditions normales de mesure 89

Annexe B (informative) Dispositifs de contrôle thermostatique 92

Annexe C (informative) Mesure de la fonction de transfert électro-optique 93

Annexe D (informative) Planification de la structure prévue de la série 94

Figure 1 – Représentation de la direction d'observation (équivalent à la direction de mesure) par l'angle d'inclinaison θ, et l'angle de rotation (azimut), φ dans un système de coordonnées polaires 56

Figure 2 – Forme du point de mesure sur le DUT pour deux angles d'inclinaison du

Figure 3 – Emplacements de mesure standard, au centre de chacun des rectangles p0 – p24 59

Figure 4 – Exemple d'inversion des niveaux de gris 68

Figure 5 – Exemple de montage normal pour les mesures de réflexion spéculaire 77

Figure 6 – Exemple d'équipement de mesure des variations temporelles 80

Figure 7 – Relation entre le signal d’attaque et les temps de réponse optiques 82

Figure 8 – Caractéristiques en fréquence de l'intégrateur (réponse de l'appareil visuel humain) 83

Figure 9 – Exemple de spectre de puissance 84

Figure 10 – Mire en drapeau à damier pour les mesures de courant et de consommation d'énergie 85

Figure 11 – Exemple de schéma fonctionnel de mesure pour le courant et la consommation d'énergie d'un dispositif à affichage à cristaux liquides 87

Figure 12 – Exemple de caractéristique de préchauffage 88

Partie 30-1: Méthodes de mesure pour les modules d'affichage à cristaux liquides –

1) La Commission Electrotechnique Internationale (CEI) est une organisation mondiale de normalisation composée de l'ensemble des comités électrotechniques nationaux (Comités nationaux de la CEI) La CEI a pour objet de favoriser la coopération internationale pour toutes les questions de normalisation dans les domaines de l'électricité et de l'électronique A cet effet, la CEI – entre autres activités – publie des Normes internationales, des Spécifications techniques, des Rapports techniques, des Spécifications accessibles au public (PAS) et des Guides (ci-après dénommés "Publication(s) de la CEI") Leur élaboration est confiée à des comités d'études, aux travaux desquels tout Comité national intéressé par le sujet traité peut participer Les organisations internationales, gouvernementales et non gouvernementales, en liaison avec la CEI, participent également aux travaux La CEI collabore étroitement avec l'Organisation Internationale de Normalisation (ISO), selon des conditions fixées par accord entre les deux organisations

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Tiêu đề	Liquid Crystal Display Devices – Part 30-1: Measuring Methods for Liquid Crystal Display Modules – Transmissive Type
Trường học	International Electrotechnical Commission (IEC)
Chuyên ngành	Electrical and Electronic Technologies
Thể loại	Standards Document
Năm xuất bản	2012
Thành phố	Geneva

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