Tobias Steinel | Instrument Systems: Can a single measurement system achieve both the speed of a camera and the spectral accuracy of a spectrometer for microLED characterization?
06:02 - 07:27
Other snippets from this talk
Summary of the clip:
Can a single measurement system achieve both the speed of a camera and the spectral accuracy of a spectrometer for microLED characterization?
To address the challenges of microLED metrology, a hybrid approach combining the speed of a camera with the precision of a spectrometer is employed. The system utilizes a camera for rapid, full-field-of-view measurements of the device under test (DUT). Crucially, a designated reference area within the field of view is simultaneously measured by both the camera and an integrated spectrometer.
The spectrometer provides the ground truth spectral data, from which highly accurate XYZ chromaticity values can be calculated without inherent error. By comparing these spectrometer-derived values to the camera's chromaticity readings for the same reference area, the system can dynamically correct or even generate a new calibration for the colorimeter. This "live calibration" ensures that the measurement device is precisely tailored to the specific spectral characteristics of the DUT, thereby maximizing accuracy and adhering to the principle of similarity.
In this short video, you can learn:
* The integration of a camera and spectrometer for display metrology.
* How a reference area enables simultaneous camera and spectrometer measurements.
* The process of calculating ground truth chromaticity from spectrometer data.
* The mechanism of "live calibration" to optimize colorimeter accuracy for the DUT.
#HybridMetrology, #CameraSpectrometer, #LiveCalibration, #SpectralGroundTruth, #MicroLED, #DisplayMetrology
This is a highlight of the presentation:
High accuracy optical metrology for MicroLED displays and wafers
More Highlights from the same talk.
01:59 - 03:44
Can we map the optical performance of 2 million MicroLEDs on a wafer simultaneously?
Can we map the optical performance of 2 million MicroLEDs on a wafer simultaneously?
Traditional LED metrology relies on single-point contacting via integrating spheres and spectrometers. However, to handle the massive density of MicroLEDs, transition to 2D camera-based imaging combined with spectrometer referencing is necessary. This approach allows developers to evaluate either electro-luminescence through contact probing or photo-luminescence by optically pumping the wafer.
By projecting excitation light onto the wafer, this photo-luminescence setup can capture and analyze up to 2 million MicroLEDs in a single field of view. The system registers every individual emitter, extracting critical metrics including luminance, dominant wavelength, coordinates, and color characteristics.
Crucially, linking the 2D camera with an optical spectrometer ensures that every spatial pixel measurement is traceable back to national standards. This combined hardware architecture eliminates the typical trade-off between throughput speed and spectral accuracy in wafer-level metrology.
In this short video, you can learn:
* How 2D imaging spectrometers capture up to 2 million MicroLEDs in one shot
* The difference between photo-luminescence and electro-luminescence wafer testing
* How spectrometer referencing ensures traceability to national standards
š **Clip Abstract** This clip highlights the transformation of MicroLED wafer metrology using fast 2D photo-luminescence imaging coupled with spectrometer referencing. By scanning millions of emitters simultaneously, the system provides traceable optical metrics for every single micro-device on the wafer.
#MicroLEDMetrology, #PhotoluminescenceImaging, #SpectrometerReferencing, #WaferLevelMetrology, #MicroLEDDisplays, #AugmentedRealityDisplays
08:11 - 09:51
Are conventional colorimeter calibration matrices causing massive errors in your MicroLED measurements?
Are conventional colorimeter calibration matrices causing massive errors in your MicroLED measurements?
Evaluating MicroLED displays presents a vastly different metrological challenge compared to legacy LCD or OLED technologies. Because micro-scale gallium nitride (GaN) structures exhibit high spatial and spectral variations, peak wavelengths shift dramatically across a single wafer or display panel.
Standard colorimeters often rely on a static unit matrix for spectral correction, which is inadequate for addressing these localized spectral shifts. Without real-time adaptation, standard measurement equipment can introduce massive measurement discrepancies, reaching up to 12 color point errors on typical MicroLED arrays.
To solve this, integrating a high-accuracy spectrometer directly into the 2D camera system allows for "live calibration" of every individual emitter. Real-time calibration reduces measurement error to under one color point, providing the precise data necessary to guide binning and repair strategies.
In this short video, you can learn:
* Why the spectral variation of GaN MicroLEDs breaks standard colorimeter calibration methods
* The risk of incurring up to 12 color point errors when neglecting live spectral correction
* How integrated spectrometers achieve sub-one color point accuracy through per-pixel live calibration
š **Clip Abstract** This clip discusses the critical need for live, pixel-level spectral calibration to counter the inherent wavelength variations of GaN MicroLEDs. It demonstrates how traditional static calibration matrices lead to severe measurement errors, whereas integrated spectrometers keep errors below a single color point.
#MicroLEDMetrology, #GaNMicroLEDs, #LiveSpectralCalibration, #ColorimeterCalibration, #DisplayMetrology, #MicroDisplayManufacturing
04:55 - 06:15
Why does MicroLED display uniformity fall apart at low gray levels, and how do we fix it?
Why does MicroLED display uniformity fall apart at low gray levels, and how do we fix it?
Performing electro-luminescence testing on the fully assembled display panel leverages the already integrated driver backplane. This configuration allows testing software to directly address and adjust individual pixels. This systematic calibration process, commonly known as "demura", is essential for correcting spatial non-uniformities across the active display area.
A major challenge in MicroLED displays is that pixel uniformity drops precipitously at low gray levels and low luminance conditions. This instability distorts the display's gamma curve and degrades image quality in dark scenes, representing a key bottleneck for high-end consumer AR/VR displays.
To combat this, specialized optical systems must be optimized to measure extremely low light levels. By reliably capturing emission profiles down to 1 millicandela and below, these systems enable accurate low-luminance demura calibration, ensuring a flat gamma response across the entire operating range.
In this short video, you can learn:
* The role of active-matrix driver backplanes in performing pixel-level demura calibration
* Why MicroLED uniformity degrades at low gray levels and low candela outputs
* How sub-millicandela measurement capabilities enable high-quality display calibration
š **Clip Abstract** This clip explores the critical process of display-level demura calibration and the hurdles of maintaining MicroLED uniformity at ultra-low luminance. It details how measuring below 1 millicandela is required to stabilize the gamma curve and achieve seamless visual uniformity.
#DemuraCalibration, #LowGrayLevelUniformity, #SubMillicandelaMeasurement, #ActiveMatrixBackplane, #MicroLEDDisplays, #AugmentedRealityDisplays