Automotive Display

Issue
Indoors and outdoors, there are many different surfaces and materials with a wide range of
reflective properties. These can be actively used in architecture and lighting design. However, there are also undesired effects, such as glare from highly reflective surfaces. One
example is solar panels on roofs or on facades, which, due to their principle of operation,
are exposed to direct sunlight at a variety of angles. In the city of Vienna, for example, a
possible impairment due to glare must be ruled out by an expert under certain circumstances
in order to obtain a permit to construct a PV system (Guideline MA 37 – 476239-2022 point
6.2). The problem quickly becomes very complex due to the wide range of different solar
cells alone, which naturally have different reflection mechanisms and properties.
Aim
The measurement of the required data for the analysis must be carried out in advance under
reproducible conditions in the dark laboratory for the corresponding solar panel(s). One possibility is to use a multi-axis goniometer to scan the complete bidirectional scattering function
(BRDF) using a light source and a spot meter. Specialized systems are available for this
purpose. However, these systems are very expensive and the measurements are time-consuming and complex. This article presents a significantly more flexible and cost-effective
method of measuring reflection properties using an imaging luminance measurement device.
Description of the innovation/»best practice«
A type-II-calibrated luminance camera (ILMD Type II) is used for reproducible measurements of such reflections. The required setup is simple and flexible thanks to an orientation
detection algorithm, making the approach well suited when switching between different
types of measurement tasks, e.g., if different angles of incidence need to be considered. In
addition, light source characteristics are easily corrected via corresponding correction measurements. This way, comprehensive data can be captured quickly. The resulting information
can then be used for further verification.
Level of realization
The presented workflow with commercially available hardware and software was validated
in a round-robin measurement.

The authors present and validate an easy-to-set up approach to measure the reflection properties of a display that can measure not only the specular, haze, and Lambertian components of display reflection, but also the diffractive component. They then research the fundamental dependencies of this fourth reflection component through a series of measurements using a variable aperture source.

Halo visibility data of measured FALD LCDs is used to test different halo perception metrics. A focus is the determination of the evaluation area as it highly impacts the setup conditions of mask-free halo measurements. Some of the metrics show an excellent correlation to human perception and can be considered as possible halo perception candidates for future studies.

We present and validate an easy-to-setup approach to measure the reflection properties of displays. It is based on a wide field of view conoscopic lens in conjunction with an orientation detection algorithm. Using this approach, we can measure not only the specular, haze, and Lambertian components of display reflection but also the diffractive component. We then investigate the fundamental dependencies of this fourth reflection component through a series of measurements using a variable aperture source and an LC and OLED display. Through these experiments, we can show that the diffractive component scales linearly with the light source's luminance and depends on the angular subtense of the light source.

The imaging luminance measurement device type II-based method is a promising way to verify the conformity of the legibility of automotive displays.

Automotive displays must fulfill high requirements including outstanding optical performance. We report on the reduction of power consumption by image enhancement improving bright readability and by local dimming of LCDs (FALD). We also address halo and non-uniformity effects for FALD, which reduce image quality, by measurements and thresholds for perception.

This paper provides an overview of image stitching and its general advantages and challenges. Further, we introduce a novel stitching concept based on our advanced pixel registration (APR) procedure. It allows easy and comparable flexible stitching setups for DeMURA and uniformity measurements in laboratory and production environments.

This contribution proposes a sparkle evaluation based on a spatial frequency filter, taking into account various setup influences. Furthermore, the effect of flexible setup conditions on the reproducibility of measurement results is investigated. The procedure and concepts are derived for sampling resolutions between 15 and 30 cpx/mm with display pixel pitches between 183 and 224 ppi and validated by a round-robin experiment with different test devices, including glass and foil-based Anti-Glare Layers. The findings serve as a basis for the measurement conditions of an automotive display sparkle measurement specification.

The alignment quality and reproducibility in ILMD (Imaging Luminance Measurement Device) based display metrology has a great influence on the reproducibility of the obtained measurement data. In this context, this contribution outlines and introduces several advanced measurement and alignment concepts that can be performed with “photometric robotics”. The term describes machine vision performed with an ILMD supported by robotic movements.

The alignment quality and reproducibility in ILMD (Imaging Luminance Measurement Device) based display metrology has a great influence on the reproducibility of the obtained measurement data. In this context, this contribution outlines and introduces several advanced measurement and alignment concepts that can be performed with “photometric robotics.” The term describes machine vision performed with an ILMD supported by robotic movements.

The increasing display sizes and changing form factors of displays, including automotive displays, lead to impractical measurement distances for spatial uniformity measurements. This contribution suggests and exemplarily applies two alternative and combinable methods to allow spatial uniformity measurements at low distances and describes an adjusted BlackMURA complaint validation procedure. The proposed methods are validated with a high-quality display device and are compared to results using the standard long-distance measurement procedure.

With increasing performance parameters and decreasing costs OLED displays are getting more relevant for premium automotive application. Therefore, the German Flat Panel Forum (DFF) extends its current LCD specification and measurement methods to also cover OLED displays. Challenges and solutions for lifetime, Burn-In (Image Sticking) and viewing angle procedures are presented more in detail.

Measurements with conoscopic lenses together with ILMDs (Imaging Luminance/Color Measuring Devices) can support the characterisation of displays and materials during the R&D and production process. Using a conoscopic lens the angular dependence of luminance/color can be measured with only a single measurement. Using different geometrical relations between the device under test, the conoscopic lens and different illumination conditions a lot of display and material properties can be measured with one or a few measurements only. The article shows the working principle of conoscopic lenses in detail. Furthermore the measurement of the angular dependent luminance/color, the angular dependent contrast and the measurement of selected angular dependent material properties (e.g. transmission and reflection characteristics of glasses) are presented. For all applications the advantages and limitations of the conoscopic lens measurements are explained to suggest the right fields of application for this measurement method.

Modern automotive displays may be sensitive to static content, which remains as an undesired effect of either temporary vanishing or being a static ghost image within the refreshed content. Therefore, there is a development of measurement procedures to quantize the degree of image sticking [1- 6]. Different aspects of these methods as the grey level dependencies or the importance of a temp-oral alignment were considered in [7]. But the mathematically necessary separation of unavoidable initial non-uniformities and the actual image sticking was excluded in that research.
This contribution concentrates on the performance of two selected image sticking evaluation methods [5, 6] from the automotive community and [1] for reference. After briefly introducing the three methods, this contribution focusses on their capability of separating initial non-uniformities from the actual sticking image effect of the target display. Therefore, a mathematical analysis, which is based on a simple but physically motivated sticking image model, is performed. Based on that, an additional non-uniformity correction is proposed. This additional correction has a positive influence on the precision but a negative influence on the measurement time of the fastest measurement method [6]. Thus, we propose a workflow, that decides based on the properties of the DUT whether the correction is necessary or not. All conclusions are supported by simulations and validated using measurement results of a randomly chosen non-uniform automotive LC display.
The aim of this paper is on the one hand to quantize the mathematical influence of the methods and on the other hands to suggest a workflow, which utilizes an existing method and optimizes its application with respect to precision and overall measurement time.

There are several optical display attributes, which require optical and photometric measurements during R&D activities or quality control and conformity assessment for automotive applications. The aim of this research paper is to assess typical properties of luminance based display measurements with respect to different optical display attributes. The measurement properties include on the one hand characteristics of the measurement equipment and on the other, the characteristics of the measurement method.
Based on the general working principle of ILMDs (imaging luminance measurement device), we briefly explain typical ILMD characteristics as well as the concepts of repeatability, reproducibility, precision and measurement uncertainty [1]. Afterwards, optical display properties as well as measurement methods [2, 3, 4] are introduced.
Finally, we qualitatively and quantitatively assess chosen influences of ILMD specifications and different measurement procedures on the obtained results.
Thus, this work shall convey a feeling for photometric display metrology requirements under the consideration of the measurement task and the desired precision

The “Uniformity measurement standard for Displays”, which is used for automotive applications, describes precise setup and alignment procedures to ensure reproducible measurement results. However, the influences of the tested device and the ILMD are not considered in detail. This contribution shows experiments and simulations to estimate these influences as well.

The requirements of automotive displays differ to a large extent from consumer and industrial displays. In order to reduce the effort in specifying and evaluating high quality displays, German automotive OEMs, Tier 1/2 and the German Flat Panel Forum have launched a cooperation.