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TU Berlin

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Ongoing Projects

Daylight Simulation in Virtual Reality

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Contact: Marina Leontopoulos, Silke Müller

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Project Description:

With advancing urbanisation a lack of daylight becomes inevitable. While the number of stress-related illnesses is increasing, the important access to daylight and nature is becoming more and more restricted. However, daylight in particular, as a clock generator of the circadian rhythm, could contribute to improved sleep quality and the reduction of stress. For all those affected, daylight simulations in virtual reality, which are independent of location, could be a substitution. In addition, the use of virtual scenes on a mobile headset offers numerous advantages in lighting research. This is particularly important for daylight experiments, which are instead realized with artificial light due to the constantly changing sky.

However, it is first necessary to clarify how exactly daylight scenes can be reproduced. One of the display-related limitations are, for example, the significantly lower luminance levels compared to the sky.

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For this reason, the perceptual parameters, such as luminance, reproducible color ranges and flicker, should be investigated as separately as possible. A clear division is made between measurements, thus characterization of the technical limitations and giving recommendations for calibration, and the perceptual psychological evaluation of these in subjective experiments. Because in the end, it is desirably to know how realistic the representation of daylight has to be in order to achieve the desired effect.

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Spectral Sky Models

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Development and Application of Spectral Sky Models in Urban planning 

Duration: 4 July 2017 – 31 May 2020

Contact: Dipl.-Ing. Aicha Diakite, Dr. Martine Knoop

Funding: Velux Stiftung

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Project Description:

The main goal of the project is the development of data-driven spectral sky models for accurate integration of daylight in the design of healthy urban structures. The spectral sky models reveal the orientation-dependent spectral characteristics of daylight and are derived from the spatially resolved spectral measurements collected at the daylight measuring station of the Technische Universität Berlin, one of the few measuring sites worldwide gathering this kind of data.

The spectral sky models will subsequently be used as a basis for a large-scale parameter study on the impact of building orientation, existing daylighting conditions and urban obstruction proprieties on the spectral potential of daylight. The spectral characteristics of daylight on facades will be displayed in spectral daylight-potential diagrams. The outcomes of the parameter study are to be shared with urban planners and lighting designers, in order to encourage greater awareness of the potential of daylight and help create new lighting design strategies that support people’s well-being.

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Marker Lights

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Adaptive and Contrast-Optimizing Street Lighting Concepts for Berlin

Duration: 1 April 2017 – 30 June 2020

Contact: Dipl.-Ing. Serkan ÖnelFarid Rahbar M.Sc.

Funding supplier: Senate Department for Environment, Traffic and Climate Protection (UVK), part-financed by the EU (ERDF Sponsorship) within the scope of BENE (Berlin program for sustainable development)

Funding Number: BENE 1053-B5-O

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Project Description:

The goal of the research project is the development and implementation of concepts for adaptive and contrast-optimizing street lighting. To achieve this, image-processing systems are to be used to illuminate either endangered objects or their direct environment if existing levels of illumination are otherwise low.

Following an analysis of the lighting situation at accident black spots in Berlin and with the aid of extensive investigations into effective recognition on the LED Walkway research facility, it will be clarified which contrast conditions are necessary and the degree to which the surrounding level of lighting can be lowered through contrast-optimizing illumination of active traffic participants.

Parallel to this, technical requirements will be formulated for adaptive illumination. Besides suitable sensors, an economic solution must be developed for a lighting unit and for appropriate controls.

The adaptive contrast-optimizing lighting concepts will be assessed step by step for safety and efficiency with the aid of a test setup on the LED Walkway. To achieve this, traffic situations will be reconstructed. In order to determine the degree to which adaptive lighting concepts can be used to change lighting to increase the attention of traffic participants, the attentive movements will be recorded with the aid of an eye-tracking system before and after installation of the adaptive systems.

Subsequently, the developed lighting concepts will be tested with a reduced level of environmental lighting on selected actual streets and junctions. In order to ensure traffic safety in test situations, close cooperation with the providers is necessary.

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Effective ipRGC Regions

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Investigations of Effective Regions for the Stimulation of Nonvisual Light Effects 

Contact: Dipl.-Ing. Kai Broszio, Dr. Martine Knoop

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Project Description:

Since the discovery of retinal photosensitive ganglion cells (ipRGC) it is possible to perform specific research on their sensitivity function and their influence on the supression of melatonin. It is now known that only a small number of retinal ganglion cells are photosensitive. It is assumed that their incidence is mainly in the lower half of the retina and that they are unevenly distributed. A higher density and sensitivity is assumed to exist in the lower part and on the side facing the nose.

Current recommendations for nonvisual effective illumination suggest the use of large illuminated surfaces. Considering the uneven distribution of photosensitive retinal ganglia cells, it is, however, questionable whether the illuminance or the melanopic irradiance at the eye, including the radiant flux from the entire hemisphere, is the correct variable for measurement in this context.

With the help of a newly developed method, under consideration of the suspected distribution of the ipRGC, the proportion (in %) of the effective radiant flux is determined in various regions of the field of vision for different light scenarios with the same light intensity at the eye. To do this, of the spatial distribution of the radiation density is recorded with the aid of a luminance density camera and weighted with V(λ) and the spectral sensitivity function of melanopsin. The results allow for evaluation of the nonvisual effectiveness of diverse illumination scenarios.

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Light scenarios (a – d typical office lighting e – f atypical office lighting situations)
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Method to determine the illumination intensity of diverse regions of the field of vision using luminance density imaging
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Simplified Daylight Sensor

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Development of a simplified, spectral
daylight sensor with directional resolution

Contact: Nils Weber M.Sc., Dr. Martine Knoop

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Daylight is generally preferred over artificial illumination. One reason for this could be the constantly changing color temperature. To record these spectral differences, every two minutes over almost the last two years, the Chair of Lighting Technology has been recording the sky's spectrally resolved radiance within the visible range, in 145 different directions (areas of the sky). In this way, the department has obtained a description of the light of the sky above the TU Berlin. The objective must, however, be to find ways of describing daylight as a light source at other locations holistically, as accurate as possible, and at lower cost.

To make this possible, a simplified roof sensor is to be developed which records the differences in luminance and the spectral composition of daylight, depending on direction. The efficiency of the new system is defined by the quality of the determination of daylight using as few individual sensors as possible.

With the help of the collected measurement data of the spectral sky scanner, diverse simplifications will be simulated. In a first step simplifications of, for example, Kobav and Chain will be simulated by summarizing the corresponding measurement values of diverse directions of the sky scanner. Subsequently, the values created in this way and the original values will be used to calculate the horizontal illuminance and the spectrally resolved vertical irradiance (for an office on model scale supplied with daylight) and to compare these with each other.

Following the development of a prototype, a suitable calibration method for daylight measurements must be designed which can be repeated in annual cycles. Finally, the measurement data of the simplified sensor shall be subject to long-term comparison with those of the spectral sky scanner. The data of the simplified sensor can be used for daylight planning and for non-visual effective light controls.

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