Optical System Structure
The optical system of the 71241 Display Color Analyzer can accurately measure a variety of display devices including flexible displays. With the help of a small and light-weight motorized shutter module, the light emitted by the DUT enters through the objective lens and then converges in the optical uniformizing module. The light emitted from each point on the area to be measured is evenly blended and then uniformly projected onto the X, Y, Z filtered sensor, saving time spent on manual calibration.
High Contrast Measurements
The Video Electronics Standards Association (VESA) has defined the DisplayHDR specifications for the display industry, ranging from the entry-level HDR400 to the high-end HDR1400 standard, with brightness ratios from 0.02cd/m2 ~ 1400cd/m2; the higher the contrast, the more realistic the image. The performance of the display is also considerably improved when built in compliance with the relevant standards. High Dynamic Range (HDR) provides high contrast display with brighter light and deeper darkness. With the growing development of LCD with MiniLED backlight, the demand for high contrast measurement is also increasing. Chroma 71241 was specifically developed to meet this need and has the ability to measure 0.001cd/m2 ~ 6000cd/m2 with contrast ratios of up to 1 million to one.
Optical Uniformizing Module
By reducing the loss of luminous flux, the amount of light available for use can be increased. This is the main factor that allows our system to achieve fast and accurate measurements in its low-brightness measurement mode. The optical uniformizing module not only achieves a uniform light distribution, but also reduces the loss caused by the transmission of the incoming light into the system, thereby optimizing the usage efficiency of the incoming light. Moreover, the sensor uses a high-transmittance Y filter and a high-sensitivity light detector to further enhance the efficiency of the amount of incoming light and achieve accurate ultra-low brightness measurement results.
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Object-Side Telecentric Optical System
The 71241 conforms to the IEC61747-6 and EIAJED-2522 standards, which recommend that the light acceptance angle be set at 5°. The 71241's object-space telecentric design enables the light acceptance angle within the measurement range to parallel the display surface being measured. As a result, the light acceptance angle of the Color Analyzer is only ±2.5° relative to the DUT’s (display under test’s) surface. Moreover, the telecentricity of the Color Analyzer, i.e. the paraxial (dimensional) error between the optical axis of the light acceptance angle and the normal line of the DUT surface, is less than 0.25°.
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Analog-to-Digital Converter (ADC)
The built-in 20 bit A/D converter greatly improves the range of luminance and chromaticity measurement with its multi-speed switching and pA precision current measurement circuit. And with the fast algorithm developed by Chroma, the measured analog values can be quickly converted into precise figures.
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Optical Measurement Software
The 71241 Display Color Analyzer is equipped with optical measurement software that captures the measurement data, saves it on a computer, and imports it into a report for processing. The included optical measurement SDK allows users to easily develop test programs to suit their needs.
Color Measurement
The digital/analog display provides 4 different display modes: xyY, TΔuvY, u'v'Y, and XYZ. The desired measurement mode can be selected according to the user's needs, and can be set to perform a single measurement or continuous measurement.
Gamma Measurement
The Gamma value is used by displays to address the difference between the brightness perceived by the human eye and the actual intensity of the light source. VESA's FPD Measurement Standard 302-5A expresses Gamma as L = aVγ+Lb, plotted in the two graphs below. The Perceived Brightness graph illustrates how the human eye responds to changes in brightness, while the Gamma 2.2 Curve graph depicts the curvature of the display output's transition from black to white. Quantitative research has shown that the human perception of brightness follows a non-linear curve—the higher the brightness level, the less responsive our eyes are to changes in that brightness. Consequently, fine-tuning the Gamma value plays an important role in ensuring the luminance of the display matches the brightness perceived by the human eye.
Gamma measurement is available for red, green, blue and white colors. In addition to the standard Gamma curve, the Gamma value and curve of each color are displayed after the measurement is completed. Users can adjust measurement color scales up to 4096 (12bit) according to their needs.
*VESA stands for Video Electronics Standards Association
Flicker Measurement
VESA and JEITA have each defined different methods for measuring the flicker level. VESA's FMA (Flicker Modulation Amplitude) method involves assessing the variation in brightness of the liquid crystal display (shown in Figure 1). The VESA FMA equation is as follows: FMA = AC/DC= Vmax-Vmin/ [(Vmax+Vmin)/2]X100%
The JEITA measurement method (shown in Figure 2) uses a luminance meter to measure the center of the screen. The data measured by the meter is sent to the filter that corresponds to the human eye's perception of flicker. The data is output to the FFT analyzer, which is then used to obtain the distribution of power at different frequencies, calculated as follows: JEITA = 10*log (Px/P0)[dB]
*P0 denotes the power spectrum at frequency 0, and Px denotes the power spectrum at different frequencies.
Figure 1
Figure 2
The Chroma 71241 Small Sized Measuring Probe complies with both the VESA and the JEITA standard, offering two flicker measurement modes: FMA and FLVL. The FMA measurement mode shows the AC/DC relationship between the change in brightness (AC) and the basic quantity (DC). The FLVL (JEITA/VESA) measurement mode separates all the different frequencies of the AC quantity, while the optical measurement software shows a graph of the flicker value of each frequency, making it easier to locate the frequency point of the generated flicker.
FMA
FLVL
*VESA stands for Video Electronics Standards Association
JEITA stands for Japan Electronics and Information Technology Industries Association
Delta E (ΔE) Measurement
Delta E (also referred to as ΔE or dE) is a color measurement standard established by the International Commission on Illumination (CIE). It uses a specific formula to convert RGB and tristimulus values into the L*a*b* color space to compare the differences between two colors. "Delta", or Δ, is a Greek letter used to represent difference or change, and "E" refers to "Empfindung", which means sensation in German. In full, Delta E refers to perceptual difference, so the measured value of Delta E represents the difference between the displayed color and the original input color. A lower Delta E value indicates higher color accuracy, while a higher Delta E value indicates a more noticeable color difference.
Chroma 71241 supports Delta E 2000 measurement. The software provides an editable list for the three primary colors (RGB) ranging from 0 to 255. This function can be used in conjunction with color gamut, gamma, and white point measurement. By setting the upper limit for Delta E, users can easily determine whether the color difference meets the specifications. Also supports measurements with standard test images from the Chroma VPG 2238.
*CIE stands for Commission internationale de l'éclairage
Color coordinate conversion diagram
Color Gamut Measurement
Provides multiple color gamut options such as B.T 2020, Adobe RGB, and NTSC. The color gamut triangles added to the color coordinates make the measured values more intuitive. After measurement, the ratio of each color gamut triangle is calculated in real-time, allowing the operator to immediately view the extent to which the DUT fills each gamut.
Color Calibration
To meet the user's calibration needs, the optical measurement software provides a special function that can directly read the values of the device to be calibrated, which eliminates the need to transcribe the data and avoids problems caused by transcription errors while enhancing the efficiency and correctness of calibration.
Test Program Editing
Test items can be programmed directly on the stand-alone unit. A program interface is also provided for users to program on a computer, and the test program can be saved for other users after editing to use without re-programming, which improves operating convenience and efficiency.
Multi-Probe Measurement
Users can use the optical measurement software on their personal computer to display measurement values in real-time, save test results, and output data for analysis. The system also supports using multiple 71241 High Accuracy Universal Measuring Probes for simultaneous measurement, as well as outputting signals in combination with a Chroma Video Signal Generator.
Stand-alone: controlled through Color Analysis Master software
1. Real-time display of measurement results
2. Supports multi-probe setup
3. Analysis of saved test data
Display Application: controlled through Video Pattern Generator 2238
1. Graphical User Interface (GUI)
2. Programmable test items
3. One-button report output
Flat Panel Display Application: controlled through GO/NOGO software
1. Auto Flicker measurement
2. Test results and graphs storage
3. Integrated signal generator and probe
We introduced the Chroma 71241 Color Analyzer in our "Built for Future Gaming Display" webinar, which focuses on the 2238 Video Pattern Generator used with the 71241 Color Analyzer for display testing. Please take a look at the video for more details.
Flicker Measurement Structure
The 71241 performs flicker measurements in compliance with the FMA (Flicker Modulation Amplitude) and JEITA (Japan Electronics and Information Technology Industries Association) measurement methods as specified by VESA (Video Electronics Standards Association). When paired with Chroma's FPD Tester series LCD module, the system can achieve completely automated flicker adjustment.
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