Fast 2D Display Testing with Spectrally Corrected Colorimeters

日付: 2022/09/27, 11:40 (EST)

Justin Blanke

場所: Detroit/MI, USA

Displays are becoming more and more prevalent in the automotive cabin and must serve a variety of functions flawlessly in a challenging environment. Specialized analysis to measure effects such as Black Mura must be conducted according to established standards; this enables meaningful comparison between supplier and manufacturer.

Our spectrally corrected colorimeters of the LumiTop series provide fast 2D measurement, ideal for the use in production quality control where short tact times have to be met.

Images are acquired, using a fast, high-resolution CMOS camera and the measured RGB values are directly transformed into the xyz color space. Combined with a highly accurate spectroradiometer, the calibration instantly adapts to the device under test for optimal accuracy during every measurement. With this working principle, all three xyz color coordinates are measured within one shot. Additionally, the color accuracy of the system is very good, due to the fact that every color coordinate is derived from the spectroradiometer. This outperforms filter-based measurement systems which suffer from filter adaption errors, especially for narrow spectral light sources like OLED or µLED displays.

For OLED or other modulated light sources, artefacts due to mismatch of exposure time and refresh rate have to be avoided. To achieve this, the modulation frequency can be easily measured with an integrated photometer and the camera can be synchronized to it.

Instead of sequential testing, many different measurements such as luminance and color uniformity, Black Mura, Gamma and Gamut can be performed simultaneously, which results in much faster testing. This makes it ideal for quality control in production with short tact times.

We will present some sample measurements performed with a LumiTop camera in comparison to a four-filter colorimeter in order to illustrate the yield in speed and therefore potentially higher throughput in production.

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