Lectures

Discover a breakthrough in microLED wafer metrology: Learn how an autocalibrating imaging light measurement system and photoluminescence microscope enable fast, contactless optical testing of millions of LEDs—with near-spectrometer accuracy in minutes.

Polarized VCSELs represent a significant advancement in laser technology, emitting light with a specific polarization orientation crucial for various applications. This paper compares two measurement methods for polarization-stable VCSELs: the traditional rotating waveplate technique and an advanced one-shot solution using simultaneous recordings from multiple polarizers.

Emerging display technologies, e.g. OLEDonSi, present opportunities and challenges in display metrology. A novel concept to achieve accurate color measurement for displays is presented. The solution is an imaging system equipped with a conoscopic lens with a wide field of view and multiple spectral reference spots to correct for spectral variations. By combining camera images with spectral data, the authors effectively characterize the angular color properties of the display.

Some display measurement tasks with imaging LMDs require evaluation of the target quantity exactly over the dimension of individual pixels, single lines, or columns of the display under test. This can be achieved by application of moving window average filtering for which the authors introduce a novel method of adjusting window parameters (i.e. kernel coefficients) to effectively remove unwanted periodic modulations even at sampling ratios close to the Nyquist limit.

Accurately measuring and adjusting near-eye displays (NEDs) in AR/VR headsets is crucial but also challenging, both during development and production. In the lab, precise measurements are needed to ensure top display quality, while in production, speed is key without compromising accuracy.

This talk compares color and luminance measurements of an NED taken with two different devices: the high-precision DMS goniophotometer, which simulates human vision but requires several hours per measurement, and the LumiTop imaging colorimeter, which captures the entire field of view in seconds while maintaining spectroradiometric accuracy. The results of both methods are analyzed and compared for an NED featuring a pancake lens with an LCD display.

Emerging display technologies such as OLEDonSi and microLED present both new opportunities and challenges in display metrology. To achieve accurate color measurements for displays with spatially inhomogeneous spectral emissions, we propose a novel measurement device. This device aims to quickly and precisely measure the angular properties of a display.

In this presentation, Instrument Systems will explore the challenges and solutions associated with measuring and examining individual microLEDs on both displays and wafers.

Instrument Systems will discuss the challenges and solutions of µLED metrology and analysis for every single µLED on displays and wafers. The focus is on high-resolution imaging light measurement devices optimized for mass production speed, photometric accuracy traceable to national standards, and flexibility for various devices under test.

Emerging display technologies such as OLEDonSi and microLED present both new opportunities and challenges in display metrology. To achieve accurate color measurements for displays with spatially inhomogeneous spectral emissions, we propose a novel measurement device. The goal of the device is to measure very accurate and fast the angle dependent color properties of a display.

When narrow bandwidth emission sources such as µLEDs are used to create full color displays, large measurement errors can occur with colorimeters calibrated against standard light sources. Experiments confirm that different calibrations of an imaging light measurement device provide different levels of color accuracy depending on the similarity of calibration source to the DUTs spectral distribution.

The significance of displays is evident in their ubiquity across technologies and industries and their footprint, growing to encompass entire device surfaces and fields of view. Display metrology provides an objective understanding of a display’s quality and performance through data, supplying tools for display innovation and evaluation to safeguard manufacturing investment.

Semiconductor lasers have become the light source of choice in many applications. IR VCSELs are widely used for sensing purposes in consumer electronics. On the other hand, longer wavelength i.e. SWIR are appearing and expected to rise.

In principle, all colorimeters need color calibration, because the color filters that are used to mimic the eye’s sensitivity to visible light will never perfectly match the theoretical CIE 1931 functions.

With the existing solutions, for VCSEL arrays it is hardly possible and timely expensive to perform LIV+λ measurements, since there are a few up to some hundreds of single emitters within the array. Furthermore, polarized VCSEL arrays are unique and have potential applications, which then require not only the LIV+λ analysis but also a polarization measurement of each emitter.

VR devices widely use multiple near-infrared LEDs for eye tracking. However, NIR illumination is potentially harmful to the human eye and skin. The international photobiological safety standard IEC 62471 provides guidelines for evaluating the photobiological hazards of incoherent broadband light sources.

The production of a Virtual Reality headset is a complex process with several steps. At each step, various measurements are taken to verify quality or to characterise the component for later use. The visual system is the key component of a VR headset and consists in general of a display and an optical lens, which form the optical module.

The upcoming μLED display technology promises high contrast, fast response time, wide color gamut, low power consumption, and long lifetime. But, the technology is challenging for optical quality control, especially for narrow bandwidth μLEDs.

Among the new display trends of the past few years, so-called curved displays have been particularly successful. Their curvature opens up a multitude of new possibilities in terms of design and application. Whether an instrument panel is perceived as pleasant, is still legible in sunlight or switches fast enough in cold winter temperatures, are parameters for individual assessment. A further quality factor is the stability of the perceived image content. For example, it is perceived as unpleasant when contrast and color change with the direction of viewing.

The 7-axis goniometer (DMS 904) expands the DMS series portfolio of goniometers to include a display measurement system that is specially geared to the above measurement tasks.

Light measuring devices (LMD) are essential tools for developing novel display technologies as well as for quality assurance in display mass production. More complex displays, e.g. Near Eye Displays (NED), might require various LMDs in different development and production phases.

Two-dimensional high-speed measurement of on-wafer. PhotoLuminescence and ElectroLuminescence and their single-pixel evaluation.

LIV curves are fundamental measurement of laser diodes to determine electrical and optical operating characteristics. LIV curves consist of L-I curves (optical intensity against current) and V-I curves (voltage against current). LIV curves determine power conversion efficiency, threshold current, slope efficiency, kinks, rollover point and more. LIV curves are widely used at various stages since it is critical to identify failed DUTs early in the manufacturing process.

The upcoming μLED display technology promises high contrast, fast response time, wide color gamut, low power consumption, and long lifetime. But, the technology is challenging for optical quality control, especially for narrow bandwidth μLEDs.

State of the art displays do have the ability to modulate refresh rate and duty cycle in order to save energy and to adapt to the display content. These features pose new challenges to display metrology equipment and may produce image artefacts. Here, we discuss the characterization and prevention of image artifacts due to the shutter type of the camera used for high accuracy display testing.

Near-Eye Displays covering a large field of view require complex optical imaging systems. While the optical system is designed to minimize distortion, residual distortion, material or production flaws lead to significant distortion. Imaging light measurement devices (ILMD) are used to detect distortion for product quality assurance. However, imaging measurement systems, especially with wide-angle lenses, may also add distortion to the measurement. Therefore, the calibration of ILMDs is crucial for the measurement of AR/VR device distortion. Here, we quantify and validate the accuracy of methods of distortion correction for an imaging light measurement device with a field of view of 120°.

Daily Poster Session from 6.00 pm - 7.30 pm

Visible and infrared light measurement devices (LMDs) are essential tools for developing novel extended reality display and sensing technologies as well as for quality assurance in the display and headset mass production. Extended reality devices come with a multitude of test requirements and the need to measure the same way as the human eye sees, and also might require different LMDs in the development and production phases.

In this EPIC Members New Product Release, our Product Manager Claudia Dippold will introduce Instrument Systems' latest CAS 140D IR spectroradiometer for measurements in the infrared range. It features the proven high measurement accuracy and reliability of the CAS140D series, recognized all over the world as a reference for wavelengths from 780–1700 nm. Compared to its predecessor model, the new CAS 140D IR offers significantly improved performance in signal sensitivity, stray light suppression and electronics.

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.

Vertical-cavity surface-emitting lasers (VCSELs) perfectly fulfill the requirements for present and future 3D sensing applications. However, to operate VCSEL-based devices in public, the manufacturer must assure “eye safe” operation compliant with the IEC 60825-1 standard or national equivalents. As VCSELs exhibit special emission characteristics that differ from other laser sources, the safety assessment is more complex, and a practical guideline does not exist.

Visible and infrared light measurement devices (LMDs) are essential tools for developing novel extended reality display and sensing technologies as well as for quality assurance in the display and headset mass production. Extended reality devices come with a multitude of test requirements and the need to measure the same way as the human eye sees, and also might require different LMDs in the development and production phases.

Next generation OLEDs displays have in principle endless contrast ratios due to their emittive nature. However, in practice OLED displays show non-uniformities at very low luminance which have to be measured and corrected in order to maintain constant contrast.

In this presentation, uniformity measurements at very low luminance will be presented and results from displays from a variety of manufacturers will be compared.

Next generation OLEDs displays have in principle endless contrast ratios due to their emittive nature and their ability to completely turn off pixels. This makes them ideal in applications that require low display luminance like use in dark/nighttime conditions.

Novel VCSEL arrays require spatial testing of the whole ensemble as well as of the single emitters in the near-field. Such optical measurements must be calibrated, corrected for polarization dependency and traceable to ensure minimum error budgets for eye safety evaluation.

Although VCSELs are intrinsically single-longitudinal mode devices, they usually show complex polarization characteristics. Most VCSEL are not designed to emit in a single polarization state, there is no control about the polarization angle. The light emitted by the VCSEL typically show a complicated polarization, even within one emitter and abrupt polarization switching can be observed when temperature or bias current is changed. In this presentation we show a method of measuring spatially resolved polarization characteristics of VCSELs. This is achieved using a combination of polarization filtered microscope optics and a CMOS camera.

Novel display technologies for AR/VR/MR devices require distinct tests to control quality during development and in production. Sharpness and contrast tests are particularly important due to the complex overlay of real and augmented images. Clear and immersive perception of the augmented or virtual reality requires optimal optical differentiation between different display contents. Typically, the modulation transfer function (MTF) acts a measure for sharpness and contrast. For accurate MTF measurement, an imaging test system should be based on a lens system that mimics the human eye system and have a similar-sized entrance pupil in front of the lens.

VCSEL-based sensor technology supports innovative applications. As VCSELs have special properties, in contrast to other typical laser sources, their characterization is more complex.

Near-eye displays (NEDs) exhibit a number of effects including distortion and sharpness distribution due to the optics that generate the virtual image. In his lecture, Dr. Cameron Hughes presents why a spectrally enhanced camera based system such as the LumiTop is ideal for fast and accurate production testing of these displays.

During the EPIC Members New Product Release, Instrument Systems' Program Manager Dr. Karthik Iyer presented our Nearfield VCSEL Testing Camera – VTC 4000.

Nowadays, the pandemic situation caused by the COVID-19 virus inspired many companies, research institutes and lighting designers to adopt UV radiation as a new tool in their projects and research. The promising germicidal effect of the UVC radiation also on the Coronavirus raises the question of the reliable measurement of the UV radiation. However, this complex task needs an expertise and appropriate equipment.

The upcoming μLED display technology promises high contrast, fast response time, wide color gamut, low power consumption, and long lifetime. However, the technology is not only challenging for mass transfer of the µLEDs from wafer to display, but also for massive parallelization of optical quality control at different manufacturing steps.

Superior properties of µLEDs for display applications challenge metrology with, e.g, narrow emission bandwidth and enormous wavelength variability depending on their electronic driving parameters. Therefore, we developed new imaging test solutions to make color uniformity measurements fast and highly accurate even for strongly varying spectral properties of µLEDs.

This short course will provide a fundamental understanding of display metrology and introduce measurement equipment and techniques. It is held in cooperation with Konica Minolta and Radiant Vision Systems.

Nowadays, the pandemic situation caused by the COVID-19 virus inspired many companies, research institutes and lighting designers to adopt UV radiation as a new tool in their projects and research. The promising germicidal effect of the UVC radiation also on the Coronavirus raises the question of the reliable measurement of the UV radiation. However, this complex task needs an expertise and appropriate equipment.

Novel display technologies for AR/VR/MR devices require advanced imaging systems to control quality during assembly and to calibrate the device. Such calibration yields an optimal match of left and right eye and allows color management for an accurate match of real world and virtual objects. For accurate measurement, such an imaging system should be based on a lens system that mimics the human eye system and have a similar-sized entrance pupil in front of the lens. Traditionally two approaches have been proposed:

Novel display technologies for augmented and virtual reality (AR/VR/MR/XR) devices, like Head-Mounted-Devices and Head-Up-Displays, require advanced imaging systems and calibration to control quality during assembly to accurately match the real world and virtual objects. We demonstrate and compare advantages of goniometric sampling spot measurements and camera based imaging solutions.

VCSELs have special properties in contrast to other typical laser sources. As a result, VCSEL eye safety evaluation is more complex and a couple of additional aspects have to be considered that would not apply for "normal" lasers. Consequently, the validation of a VCSEL's laser class is not trivial, and even more so because an easily understandable guideline for the assessment of VCSEL safety has not yet been published.

Date: December 2, 2020

Time: 17:15 (CET)

LpS Digital 2020

China International Optoelectronic Exposition

IEEE OGC Conference

Virtual Event

Friday, September 11, 2020

Photonics Germany @ CIOE 2020

Date: September 10, 2020

Time: 1 pm – 5 pm Shenzhen

Location: World Exhibition & Convention Center ∙ Conference Room 2, Hall 1

SID Display Week 2020, virtual event

Spatial Uniformity Display Measurement, Session 71.3

Thursday, August 6, 2020

SID Display Week 2020, virtual event

Display Measurement Standards I, Session 50.3

Thursday, August 6, 2020

edc 2020

Nuremberg, Germany

Wednesday, 26 February 2020, 16:35 - 16:55, Session 6 Display Glass & Measurements

SSL China 2019

Tuesday November 26, 2019 11:40am

Shenzhen Convention and Exhibition Center (5th Floor Peony Hall), China

Lux et Color Vesprimiensis

Völgyikút Ház, Veszprém, Ungarn

Thursday, 10 Oktober 2019, 5:20 pm

LED professional Symposium + Expo

Seestudio, Opera House Bregenz, Austria

Thursday, 26 September 2019, 11:30-12:00 am

SID Vehicle Displays and Interfaces 2019

Burton Manor Conference Center, Livonia, MI, USA

Wednesday, 25 September 2019, 9:15 – 9:35 am, Session 5.4

EuroDisplay 2019

Minsk, Belarus, Stork Room 1, O-43

Thursday, 19 September 2019, 10:05 am, Session 7

SID Display Week

San Francisco Moscone Center, CA, USA, Room LL20A

Session 50.1, Co-Chair: Jürgen Neumeier (Instrument Systems GmbH)

Thursday, 16 May 2019, 09:00-10:20 am

ICDT International Conference on Display Technology 2019

Kunshan, Suzhou, China

Thursday, 28 March 2019, 5:40 -6:00 pm