Lightlab

The “artificial sky” is a special element of the light laboratory and represents a technical masterpiece from the 1970s. The room, measuring 3 x 3 meters, is precisely aligned with the four points of the compass. The backlit stretch ceiling realistically reproduces the brightness and color temperature of a cloudy sky.

The fall of light from the zenith to the horizon corresponds to the natural impression of an overcast sky. In addition to diffuse sky lighting, the sun can also be simulated. Using a parabolic mirror, a 100-watt bulb projects almost parallel beams of light onto a central table on which, for example, a room model can be placed. The light source is mounted on a movable arm that can simulate different positions of the sun under computer control.

Various solar patterns can be simulated, such as summer and winter or the different conditions at the North Pole compared to the equator. These processes are reproduced in fast motion - a complete summer day in Detmold, for example, lasts around five minutes, which corresponds to a 15-fold acceleration. With the help of a model, it is possible to clearly see what influence different lighting conditions can have on the interior of a building.

The “artificial sky” in the light laboratory thus enables a precise analysis and visualization of light phenomena and offers valuable insights into the effect of light in an architectural context.

The room-filling matt black free-standing “near-field goniophotometer” can be used to measure the spatial luminous intensity distribution, the direction-dependent luminance and the spectral composition of a light source up to 600 mm in size using a highly sensitive measuring camera, a spectrometer and photometer.

The measurement results are used, for example, in the form of luminous intensity distribution curves to simulate lighting situations. The device makes a valuable contribution to teaching and research.

The “integrating sphere” is part of a measuring device that can detect the entire luminous flux of even a larger light source within a very short time. For measurement, the light source is fixed in the center of the two-part sphere. The emitted radiation is homogenized by an extremely matt, barium sulphate-coated, highly reflective white inner surface of around 10 m and guided to the spectrometer through a small opening via an optical fibre. This is where the actual evaluation of the radiation takes place: Radiant power in the range of 360 - 1020 nm, total luminous flux, color temperature, color location, color rendering, in which spectral range how much power is present, etc. In combination with the goniophotometer, all the photometric data of lamps and luminaires that are required in simulation programs can be recorded.

The skylight-like window in the ceiling gives the impression that you are looking into the bright blue sky. However, this is an artificial imitation by the company “Coelux”.

The construction built into the false ceiling, consisting of an optical system of mirrors, lenses and 300 watt LEDs, created this depth effect. The flat, window-sized panel is made of a material that diffuses the artificial light in the same way as our atmosphere. This is why the “view” appears sky-blue, although it is actually a large black box. The “sunlight” is yellowish-white as usual and the shadow is slightly bluish due to the scattered light.

Our artificial sun was already part of an internal university study with the research objective “How does the (artificial) sunlight influence the perception in the work environment?”