Disposal of discharge lamps. Osram HQI-E 150 W/NDL CL
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And so we distinguish between the visual path, responsible for all visual tasks such as recognizing pictures, perceiving brightness, contrast, shapes, etc., and the non-visual path, or also “biological path”, which controls in particular the circadian rhythms and also influences in the daytime our alertness and mental performance and also biological functions such as hormone production, the blood circulation and the metabolism.
The non-visual path is essentially independent of the visual path.
Light circadian function visual sensitivity wavelength [nm] standardized by the CIE.
Non-visual path
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Cirkadian rhythm
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Alertness
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Tiredness
• Hormone production
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Vitality
• Recovery
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Blood circulation
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Metabolism
Visual path
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Recognizing pictures
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Brightness, illuminance
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Contrast
•
Shapes
• Movement
•
Perception
•
Information
8.4 UV radiation
The metal halide lamp standard IEC 61167 describes the effective UV-radiation output and specifies limit values in the respective lamp data sheets. This means that the UV radiation of the lamp in the range
250 – 400 nm is weighted with a so-called evaluation function (see figure 55) (similar V(λ)-evaluation of visible radiation).
Scientific studies (Prof. Brainard, Thomas Jefferson
University, Philadelphia) have established that melatonin suppression depends not only on brightness but also on the wavelength of the light used. Light in the blue spectral range of about 460 nm has the strongest effect on suppressing melatonin.
This evaluation curve shows the generalized sensitivity of human tissue to UV radiation over wavelength and has been defined by the ICNIRP (International Commission on Non-Ionizing Radiation Protection).
The course of the sensitivity curve measured by Brainard for melatonin suppression shows no correlation to the course of the previously mentioned eye sensitivity curves for the red, green or blue photoreceptors in the eye.
This evaluation curve is used today by nearly all national and international bodies (standardization, professional associations, etc.). The ACGIH (American
Conference of Governmental Industrial Hygienists) uses this evaluation for workplace guidelines.
This made it apparent that there is a further previously unknown type of light-sensitive cell in the eye responsible for the circadian effect of light.
The NIOSH (National Institute for Occupational Health and Safety) is an American federal authority that researches occupational health and safety and issues corresponding recommendations.
Prof. Gall from the “Lichttechnisches Institut” at the
University of Ilmenau has recognized that the sensitivity curve for melatonin suppression published by
Brainard is very similar to the known curve V(λ) which describes eye sensitivity for seeing brightness. Only the spectral position is shifted towards blue.
The curve C(λ), suggested by Gall, serves today as the foundation for a measuring system for circadian lighting data, defined in DIN V 5031-100. These weighting factors can be taken into account in order to consider the biological effect of light sources.
The maximum daily dose (8h working day) permitted according to the ICNIRP is 30 J/m². With a mean illuminance of 500 lx, this dose is achieved with an effective UV radiation of approx. 2 mW/klm. The IEC 61167 data sheets for metal halide lamps indicate the maximum values of the generated effective UV radiation.
IEC 62035 states the limit values for UV radiation
(2 mW/klm resp. 6 mW/klm) for high-intensity discharge lamps as an indication for the luminaire manufacturer.
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