2015 - now

The best of two worlds - Combining goniophotometry and digital image processing

Licht 2016
Goniophotometry allows the measurement of high contrast distributions like headlamp low beam, rear lamps or other high dynamic distributions and has a very slow mismatch factor. But the measurement is slow and takes minutes up to hours for a complete distribution. Digital image processing is fast and provides a distribution in high resolution in few seconds. The solution for the customer is a combination of the speed and possibilities of digital image processing with the contrast and accuracy of a goniophotometer.

Authors

  • Christian Schwanengel
  • Franz Schmidt
  • Thomas Reiners
  • Carsten Diem

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Zukunftssicher und korrekt Messen

Solid State Lighting (SSL)-Leuchten (LED, OLED, PLED) stellen höhere Anforderungen an die photometrische Messtechnik. Kamerabasierte Goniophotometer (Nahfeldgoniophotometer) bieten hier wesentliche Vorteile gegenüber klassischen mit Einzelsensoren messenden Systemen (Fernfeldgoniophotometer) und sind auch für zukünftige erweiterte Messaufgaben gerüstet. Der folgende Beitrag erläutert beispielhaft erweiterte Möglichkeiten zur realitätskonformeren UGR-Blendungsbewertung und für Simulationen von Beleuchtungssituationen. Weiterhin wird die Thematik der für Fernfeldgoniophotometer relevanten photometrischen Grenzentfernung beleuchtet.

Authors

  • Knut Bredemeier
  • Udo Krüger
  • Franz Schmidt

Invited Paper: Recent Standardization Efforts and Measurement Procedures of German Automotive OEM and German Flat Panel Forum (DFF)

Society for information display (SID) international symposium 2016
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.

Authors

  • Karlheinz Blankenbach
  • Udo Krüger
  • Hans-Ulrich Lauer
  • Martin Zobl

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Pixel Crosstalk: A New Metric to Characterize DOI Loss Due to AG Treatments of Display Glasses

Society for information display (SID) international symposium 2016
A method is proposed that characterizes the loss of image clarity caused by anti-glare coatings. The method uses high resolution imaging, giving a distribution of scattered light that can be related easily to the clarity impression of the human eye. Results of different AG treated cover glasses are shown and a new parameter is proposed to characterize the loss of image clarity. This can be applied to the specification and characterization of the cover glasses as well as the characterisation of the final product for quality assurance.

Authors

  • Thomas Fink
  • Udo Krüger

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Image Blurring Induced by Scattering Anti-Glare Layers

Society for information display (SID) international symposium 2016
We introduce the scattering-induced spreading of a narrow linear light source in transmission as an alternative method for characterization of image blurring induced by anti-glare layers. This novel method is compared to the recently presented concept of pixel crosstalk and to the transmissive scatter distribution function of anti-glare layers measured in two different ways. The reduction of transmittance modulation is presented as an additional method for characterization of image blur. The ranking of the results is compared to a generalized haze level of the AG samples as obtained from the transmittance distribution functions measured with two different methods.

Authors

  • Michael E. Becker
  • Thomas Fink
  • Udo Krüger

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Diskussion von systematischen Effekten beim Betrieb einer Hyperspektralkamera

Fachbeitrag DfwG Jahrestagung 2015
Die vorliegende Arbeit beschäftigt sich mit Einflussgrößen welche beim Einsatz einer Hyperspektral-kamera berücksichtigt werden müssen. Diese Einflussgrößen können direkt aus den Eigenschaften der verwendeten Filtertechnologie abgeleitet werden. Die betrachtete Hyperspektralkamera besteht aus einem elektrisch durchstimmbaren Filter (Liquid Crystal Tunable Filter LCTF) zur spektralen Zerlegung des Lichts, einem abbildenden optischen System und einem Matrixdetektor. Aufgrund dieses Aufbaus kann, bei entsprechender Kalibrierung, das Spektrum einer Lichtquelle ortsaufgelöst ermittelt werden. Die ortsaufgelöste Messung des Spektrums einer Lichtquelle erfolgt bei der vorliegenden Hyperspektralkamera nach dem Monochromatorprinzip, das heißt das Spektrum der Lichtquelle wird sequenziell abgetastet, man spricht hierbei von der Zerlegung des Spektrums in sogenannte Kanäle. Die Kanäle der Hyperspektralkamera besitzen Bandpasscharakter und sind quasi kontinuierlich (große Kanalanzahl) über den spektralen Arbeitsbereich des Systems verteilt. Die Bestimmung von farbmetrischen Größen erfolgt über das Spektralverfahren. Wesentliche Einflussgrößen beim Betrieb einer Hyperspektralkamera sind die endliche Bandbreite der Kanäle, der eingeschränkte Arbeitsbereich (400 nm – 720 nm) und das winkel- und temperaturabhängige Transmissionsverhalten der verwendeten Filtertechnologie. Der Einfluss sowie mögliche Korrekturen dieser Einflussgrößen werden in der vorliegenden Arbeit, anhand der Bestimmung von farbmetrischen Kennwerten von LEDs, untersucht.

Authors

  • Benjamin Ruggaber
  • Udo Krüger
  • Franz Schmidt

Determination of tailored filter sets to create rayfiles including spatial and angular resolved spectral information

Optics Express 23(23):29543 · November 2015
To simulate and optimize optical designs regarding perceived color and homogeneity in commercial ray tracing software, realistic light source models are needed. Spectral rayfiles provide angular and spatial varying spectral information. We propose a spectral reconstruction method with a minimum of time consuming goniophotometric near field measurements with optical filters for the purpose of creating spectral rayfiles. Our discussion focuses on the selection of the ideal optical filter combination for any arbitrary spectrum out of a given filter set by considering measurement uncert-ainties with Monte Carlo simulations. We minimize the simulation time by a preselection of all filter combinations, which bases on factorial design.

Authors

  • Ingo Rotscholl
  • Klaus E. Trampert
  • Udo Krüger
  • Cornelius Neumann

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Comparison of luminous intensity distributions

Lighting Research and Technology, November 4, 2015 | 62-83
Luminous intensity distributions enable an evaluation of the spatial radiation characteristic of a light source. This radiation characteristic is determined by the structural properties of the light source, its operating parameters and the properties of the measuring system. This paper describes some possible methods and rules for comparing luminous intensity distributions. The focus is on the development of calculation rules for quantifying the differences between two luminous intensity distributions. The difference measures developed allow the user to establish an objective comparison between luminous intensity distributions, this comparison being completely independent of the measuring system, the properties of the luminous intensity distributions and the users themselves. Further, the dependence of the properties of luminous intensity distributions resulting from measurement practice, such as adjustment uncertainties, regions that cannot be covered or measured, deviations of the total luminous flux, data noise and resolution differences, are discussed, and appropriate pre-processing and correction steps proposed. In addition, various visualisations of the differences between two luminous intensity distributions are demonstrated and the functionality of the difference measures developed is documented.

Authors

  • Frank Gassmann
  • Udo Krüger
  • Tony Bergen
  • Franz Schmidt

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Entwicklung einer Hyperspektralkamera unter Verwendung einer Filtertechnologie mit stark vom Einfallswinkel des Lichts abhängigem Transmissionsverhalten

Tagungsbeitrag Lux junior 2015
Die vorliegende Arbeit beschäftigt sich mit Einflussgrößen welche beim Einsatz einer Hyperspektral-kamera berücksichtigt werden müssen. Diese Einflussgrößen können direkt von den Eigenschaften der verwendeten Filtertechnologie abgeleitet werden. Alle Betrachtungen beziehen sich auf die Zielsetzung, farbmetrische Kennwerte von LEDs, unter Verwendung einer Hyperspektralkamera, zu bestimmen.

Authors

  • Benjamin Ruggaber
  • Udo Krüger
  • Franz Schmidt

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Ist eine objektive Beschreibung der Störempfindung bei künstlicher Beleuchtung möglich?

Zeitschrift LICHT 7/8 2015, S. 70-74
Die visuelle Erfassung von Information durch das menschliche Auge kann durch helle Lichtquellen gestört werden. Diese Effekte werden unter dem Sammelbegriff der Blendung zusammengefasst. In diesem Beitrag wird diskutiert, ob zum einen die Simulation und Vorhersage eines belastbaren Blendungsurteils und zum anderen die messtechnische Überprüfung einer realen Beleuchtungssituation anhand der vorhandenen Messdaten, Messmittel und Messmethoden überhaupt möglich sind. Dabei wird auf aktuelle Arbeiten zur messtechnischen Bewertung von subjektiven Blendungsurteilen in Innenräumen Bezug genommen.

Authors

  • Tobias Porsch
  • Carsten Funke
  • Christoph Schierz
  • Franz Schmidt

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Measurement of the Unified Glare Rating (UGR) based on using ILMD

Proceedings of the 28th Session of the CIE, Manchester; Vol. 1
Imaging luminance measuring devices (ILMD) are widely used in different fields of application. The assessment of glare caused by sun light and technical lighting installations for outdoor and indoor applications has meanwhile become reality. Measuring the discomfort glare for artificial indoor lighting installation is a fixed requirement of current standards. The aim of this study is to develop a simple and very well suitable software algorithm to fulfil those requirements by using the ILMD measuring technique comfortably. This paper also includes a comparison of currently existing equations for the discomfort glare regarding their technical requirements to be met by the ILMD and also the validation of new ideas and methods for analysis and evaluation. Keywords: Unified Glare Rating (UGR), Imaging Luminance Measuring Device (ILMD), discomfort glare

Authors

  • Tobias Porsch
  • Carsten Funke
  • Christoph Schierz
  • Franz Schmidt

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Analysis of errors associated with photometric distance in goniophotometry

Proceedings of the 28th Session of the CIE, Manchester; Vol. 1
In lighting calculations and simulations, the emission of a light source is conventionally modelled using the far-field intensity, also termed luminous intensity distribution (LID). Previous studies have indicated that the traditional limiting photometric distance, to reach far-field conditions, is not always easy to determine. The limiting photometric distance, also called the photometric limiting distance of a light source is the shortest distance between the reference plane of a light source and the effective reference plane of a photometer, for a given acceptable error considering the photometric inverse square laws (ISO/CIE 19476:2014, 2014). This distance is dependent on the size of the light source, the luminous intensity distribution (beam angle), the spatial luminance distribution and the predetermined acceptable measurement error. In this paper the problems are analysed in detail for a disk-shaped light source, a linear light strip and a worst case scenario using two small (point) sources separated by a certain distance. The limiting photometric distance is investigated using different measures of error - not only for the main illumination direction but also at different angles of emission.

Authors

  • Valéry Ann Jacobs
  • Peter Blattner
  • Yoshi Ohno
  • Udo Krüger
  • Peter Hanselaer
  • Patrick Rombauts
  • Franz Schmidt

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Traceability of a CCD-Camera System for High-Temperature Measurements

International Journal of Thermophysics 36(8) · June 2015
A CCD camera, which has been specially equipped with narrow-band interference filters in the visible spectral range for temperature measurements above 1200 K, was characterized with respect to its temperature response traceable to ITS-90 and with respect to absolute spectral radiance responsivity. The calibration traceable to ITS-90 was performed at a high-temperature blackbody source using a radiation thermometer as a transfer standard. Use of Planck’s law and the absolute spectral radiance responsivity of the camera system allows the determination of the thermodynamic temperature. For the determination of the absolute spectral radiance responsivity, a monochromator-based setup with a supercontinuum white-light laser source was developed. The CCD-camera system was characterized with respect to the dark-signal-non-uniformity, the photo-response-non-uniformity, the non-linearity, and the size-of-source effect. The influence of these parameters on the calibration and measurement was evaluated and is considered for the uncertainty budget. The results of the two different calibration schemes for the investigated temperature range from 1200 K to 1800 K are in good agreement considering the expanded uncertainty (k=2). The uncertainty for the absolute spectral responsivity of the camera is 0.56 % (k=2).

Authors

  • L. Bünger
  • K. Anhalt
  • R. D. Taubert
  • Franz Schmidt

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Medição de luminância por meio de imagens para avaliação do ofuscamento

A medição do incremento limiar, ou seja, da perda de visibilidade causda pelo ofuscamento, será uma exigência das normas futuras. Atualmente, o ofuscamento causado por instalaçoes de iluminação artificial ou plea luz natural já tem sido avaliado tanto em aplicaçoes internas quanto externas. Exte artigo descreve uma ferramente de software que utiliza dispositivos de medição de luminância por meio de iamgens para medir o incremento limiar.

Authors

  • Tobias Porsch
  • Andreas Walkling
  • Andreas Überschär
  • Christoph Schierz
  • Franz Schmidt