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UMaster-MS Applications

Spectral reflectance

Absolute spectral reflectance is require in many situations. Combined with a stabilized white source UMaster-MS can provide easily absolute spectral reflectance in the visible range of any object. Accuracy of the system has been checked using a color checker with 24 different zones of well controlled color and spectral reflectance . The measurement is made using a stabilized white LED illumination. The non-homogeneity of the illumination is corrected making the same measurement on a white reference. The spectral reflection of each zones is then computed taking white zone (19) as reference. Some results are reported hereafter compared to the theoretical spectral reflectance provided by the color checker constructor. Agreement is excellent is quasi all the cases.

Spectral reflectance of different zones (points) compared to theorical spectra (lines): zone 19 (white) is taken as reference

Color checker

Color checker illuminated with white LED

Spectral reflectance at three different wavelengths

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Radiance of blue LEDs at 459nm

Emission peak adjustment of blue LED using Pearson VII model

Mean wavelength and wavelength band pass for all the blue LEDs of a tile

LEDWall analysis

Due to statistic LED emission dispersion, all LEDWall tiles generally require a colorimetric calibration. This can done using color measurements of each type of LED (generally blue, green and red). Automated procedure have been developed for ELDIM UMaster videocolorimeter. UMaster-MS allows more in depth analysis of LEDWall emission.

Emission spectra of each LED can be measured directly and mean wavelength emission λ_m and wavelength band pass Δλ_m can be deduced. For the multispectral imaging measurement, each emission spectrum is extracted and adjusted using a Pearson VII law:

M is a shape parameter that is fixed to 1.6 for LED emission spectra. Detailed emission properties of one LEDWall tile can be deduced. In addition to allow luminance and color correction spectral information are useful to understand and reduce the emission imperfections.

Correlation between mean wavelength and wavelength bans pass for 1024 blue LEDs of a tile

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Reflective display & aspect

UMaster MS can provide full spectral characterization of reflective displays. Global spectral reflectance homogeneity can be checked. The display image aspect can be also predicted under any illumination conditions.

Spectral reflectance homogeneity UMaster MS is capable to provide high spatial resolution spectral information and not only luminance and color measurements. On reflective displays and after normalization with a measurement on a white reference under the same illumination conditions, the spectral reflectance homogeneity can be checked. Diffusion defects can be also easily detected.

Image aspect under various illuminants Absolute spectral reflectance for a given image using the reflective display can be measured. Then the display aspect with this image and any type of illumination can be calculated and predicted.