Daylight is our greatest natural source of light during the day and the moon at night.
Light is the eye for the visible part of the spectrum. Light is a wave motion and is expressed in wavelengths (nm). Because visible light always travels through a medium, it will not appear in frequencies. In general, the medium is air, but it can also be a transparent liquid or solid.
The wavelengths for the eye visible light are located between 380 nm (violet) and 780 nm (red).
Ultraviolet (smaller than 380 nm) and infrared (greater than 780 nm) are not visible but detectable, both through the eyes and through the skin.
(see radiation and magnetic fields ).
Daylight
Receiving light through our eyes and skin is a necessary element for equating our biorhythms. In addition, has a positive influence on the performance efficiency of the human being to work. Daylight and exterior views (especially the green of plants and trees) has a stimulating effect on performance and well-being of man. In hospitals gives daylight and exterior views faster healing. Here applies: the more southerly directed the shorter the recording time.
Daylight also has its limitations. Excess light level gives light pollution by the users include working with machines and monitors. It is therefore necessary here adequate light resistance with a high LTA value, which does not mean: light-tight. Sunlight, must be able to continue to experience the user.
Daylight Protection, the user needs to need and necessity, preferably electric, can operate. In addition to light-security has light resistance also has a heat-resistant operation, so energy-saving advantage. This section is central (electric) to be controlled by a seperate or the building management system. This allows the heat / cold insulation can be used at times when there are no people in the building. Adequate light barrier has a matte-reflective metallic exterior and may be in (twin) pleated, vertical or horizontal blinds.
Artificial light
With daylight we just do not make it. Artificial light as a supplement or replacement of daylight will therefore always be necessary. Fluorescent lighting (fluorescent or compact (savings) lamps is the most used. The use of incandescent and halogen lamps is restricted by the European Commission because of the unfavorable light energy efficiency. The light output is only 5% compared to total assets.
As a replacement for incandescent and halogen lamps, the LED lighting is appropriate. The development of LED and OLED lighting is going at a fast pace, so happy the quality of the lighting is improving. It should still be a critical look at the achieved level of light, the right color, the energetisch- and maintenance efficiency and electrical and fire safety. To qualify for investment are stringent energy requirements per fixture (100-110 lumens / Watt). It is unfortunately only look at the horizontal illuminance on the worksheet. It ignores the human communication and interaction necessary vertical illuminance.
norms
The standard for visible light that used in the design and evaluation of lighting situations: BS EN 12464-1: 2011 Light and lighting - Workspaces; Part 1: Workspaces inside. This harmonized European Standard (EN) is for many specific tasks and areas to the correct horizontal and vertical illuminance levels indicated, suplemented with a value of good color reproduction factor for uniformity and value in order to prevent glare interference from the luminaire (see other in VDU ). Also, pay attention to the prevention of light pollution and also sufficient vertical illumination. The latter is important for proper observation of persons, obstacles and experience of the (work) space and objects within that space.
Because this standard is mostly technically oriented, the Dutch Foundation for Illumination (has www.nsvv.nl ) released an explanation of this standard, "Notes to BS EN 12464-1," and also practice documents for further clarification issued for ao lighting School, office lighting, museum lighting and industrial buildings.
In addition to the standard BS EN 12464-1: 2011 also applies BS 3087: 2011 Ergonomics - Visual Ergonomics: background, principles and applications. The use of this standard is to focus on getting good information about brightness relationships between work surfaces (including the screen) and its surroundings and to color and size (read) signs and symbols in relation to see and observe.
Many complaints about improper lighting can be reduced by reflective surfaces, too much and too much brightness ratios, a low color contrast, light pollution into the field, because we are "too straight" and are affected by the light above us rather than our natural posture in which the 20 ° head is directed downwards.
To measure light levels and brightnesses, the NEN 1891 an important guideline.
In addition to measuring horizontal illuminance, this standard also gives tools for measuring vertical and cylindrical illumination, measuring diffuse and peak luminance, determining luminance ratios and diffuse reflectance.
Carrying out a proper measurement is work experts. So take this one lightly consultant with knowledge of light measured in accordance with DIN 1891 in the arm.
Important - also for an indicative measurement - is in any case, that one determines the average of at least 20 over the plane divided light measuring points.
risks
Peak Clear Present luminaires with specular reflector forms a major source of light pollution complaints. Despite these fixtures comply with the so-called UGR factor of 19.
Large differences in brightness (luminance) can cause discomfort and sometimes dangerous situations, such as glare, flare, scrambling. This allows signals (warning) signs disappear and text can be unreadable. Think about escape routes and emergency response transparencies or stop signs. Both daylight (eg. Escape on transparent glass door) and artificial light (spotlight) may be the problem.
The maximum recommended brightness difference in the visual field is between 1:10 workspace (including the screen), walls and ceiling and between 1:30 workspace / screen and window (including light resistance). The frequent need exceeding these ratios may increase the risk of getting ocular and headaches. Discomfort reduces work performance efficiency.
dazzle
Brightnesses larger than 5000 cd / m 2 giving an absolute blindness. Great background brightnesses not only lead to blindness, but also ensure silhouette formation. As a result, one can not perceive information, which may be risky. In silhouette form, one can not detect faces and facial expression. This gives a strong sense of social insecurity.
Too much light on the work surface or display is a scrambling of information that it is not perceptible. This shall include as one with the laptop on a sunny day is out of work. The phenomenon is not only very annoying, it also lowers the performance efficiency and may even be dangerous and / or financial loss, for example if one can not read warning information.
The visible light can be harmful to the eye at a very high level, such as in direct sunlight or bright lights, even LEDs (have to) look and lasers. Prolonged and permanent damage occurs at a dose effect (product quantity and time) 10 8 cd.s / m 2 corresponding to a brightness of 10 9 cd / m 2 at a viewing time of> 0, 1s. In general, must magnitudes greater than 3000 cd / m 2 can be prevented.
Bright light at one focal point may lead to partial failure in the yellow spot (macula / fovea). Such a phenomenon can occur with dentists as a result of watching a prolonged period (stare) to the 'hole' in the tooth.
Although many still think so, the light from fluorescent lamps (fluorescent tubes and compact lamps) is not harmful. For some, the blinking frequency of the fluorescent lamp (especially visible at the ends of the tube with conventional ballasts (ballasts) 50Hz) very annoying and can cause headaches. The problem with the blinking frequency and headaches also applies to a large number of LED lamps and LED light fixtures with inaccurate rectified (ripple voltage with ripples of 50Hz) and voltage lowering electronics.
Color temperature and color rendering
When lighting, and LED lighting in particular, attention should be paid to proper color temperature and correct -natuurlijke- color rendering (Ra> 80). Illumination with a color temperature between approximately 2000 and 3000K gives a warm tint in the red / yellow area. When a color temperature of 4000K the above, one speaks of cool colors. The higher the value, the color temperature of the cooler (blue to whitish) color.
Daylight (measured with a cloudy sky on April 30 at 12.00) has a color temperature of 5700K. Colour temperatures of light sources (LEDs) with more than 6000K give mostly a blue-gray color and is not equivalent to daylight.
Many LED bulbs have a limited spectral distribution. Poor LED bulbs have about large share in the blue part of the spectrum and a lack of green / yellow and low in green and red part. Ostensibly, it seems okay, but the natural color reproduction, and specifically those of the skin is unbalanced and false.
The color rendering factor / index (Ra) indicates the reference to the natural color. A color rendering factor (Ra) of 100 is equal to daylight and heat emitters such as light bulbs and is the best. Good fluorescent lamps have an Ra of 90 or 80. color and / or quality assessments is a high color temperature (> 5000K) with an high color rendering (Ra> 90). However, the color reproduction factor is an arithmetic mean and can still miss parts of the spectrum in spite of a high value.
LED-lighting
There is good LED lights, but unfortunately there's too bad LED lighting. Excellent LED lighting covers the entire spectrum and has an Ra> 80 and a ripple <2%. Poor LED lighting has an Ra of mostly (still) around 60, and that's bad. In addition, such an LED lighting only in the middle of the white light source and color distortion occurs at the edges on. It is also often does not reach the whole spectrum, but its color temperature the average of the two extremes, namely 6000K and 2500K. The total light output of LED retrofit fluorescent tube lamps is sometimes lower than comparable fluorescent lamps, which is also another descending.
The thermal management of LEDs is particularly important. Can the heat away to the rear of the LEDs insufficiently good airflow, then the probability of 80% that these early, and if the light level drops sharply. Energetic give LED lighting next to a poor power factor of 0, 2 also higher harmonic voltage surges. Retro-fit LED tubes often give a downward light and the workspace as well not lit the faces of people. The standard of good lighting BS EN 12464-1 also indicates that the vertical illuminance should be around 60% of the horizontal illuminance.
So at 500 lux horizontal illuminance vertical illuminance should be about 300 lux. In short, keep in LED lighting currently accounts for energy efficiency, maintenance and longevity. Replacing office lighting LED lighting begins to get a seat, but the facility manager should have an independent assessment of lighting, electrical, energy and maintenance performance. Moreover, LED lighting can already be well used in halls, corridors and elevators and other places where non-critical lighting can be used.
T5
Conversion to T5 fluorescent tubes using 'socks' demands extra attention. The placing of the with "socks" provided for T5 lamps in existing fixtures give a reduction of the illuminance with respect to the original design by at least 10%. In many situations it is only right below the standard level. In addition, a safety expert warning still applies. Not only is a "bootee" placed in front of the T5, but also the lighting fixture is being converted.
Hits a T5 tube with 'sock' defect, one should not stand FL-tube places in the luminaire, because then the control electronics can fail and potentially could catch fire. The conversion causes a deviation from the original construction of the fixture and thereby void the warranty of the luminaire. Also meet converted luminaires (also applies to retrofit led tubes) no longer meets the CE Mark.
ultraviolet light
Ultraviolet light is also the exception of solar radiation released during welding, curing processes (dentist) in the printing industry and in the packaging (see radiation and magnetic fields ). Somewhat depending on the power, the aanstraaltijd and wavelength (the whole is called 'dose effect'), there are effects as suntan acute eye problems (actinic conjunctivitis or snow blindness) or chronic eye problems (cataracts) possible. For long-term exposure to much UV light the skin will age faster and the risk of various types of skin cancer present increased, especially in people depigmented. Note to UV light - but also in bright blue light - the specular reflection of light. The reflected to UV and blue light cause damage to the eye and does not affect the operation in our biological system by the action in the brains.
Shielding of the source and / or the cover of his skin and eyes, depending on the situation, the appropriate forms of protection. Unfortunately, in many industrial situations or improperly shielded the UV sources. Especially welding often gives eye damage (arc eye) and sometimes - fortunately no lasting - complaints from tanning and / or incineration.
Ultraviolet light is divided into:
UV-A
(320 - 420 nm)
UV-B
(280 - 320 nm)
UV-C
(10 - 280 nm)
Infra-red
Having this is not expressed in nanometers (nm) on the size of this wavelength, but in micrometers (microns).
The infrared wavelength is divided into:
Short-wave IR (IR-A)
.780
3 microns
Medium wave IR (IR-B)
3
50 microns
Long-wave IR (IR-C)
50
1000 microns
The basic effect of infrared is heat and thus leads to thermal damage to the skin or eyes. The penetration depth of optical radiation in both the skin and the eye is dependent on the wavelength: "the longer the wave, the greater is the depth of penetration".
Caution should be to include halogen spotlights with a so-called cold light mirror. This mirror allows to increase the service life of the lamp, by the non-visible heat in the form of infrared radiation. For a long time by looking at a mirror such as a halogen lamp is in operation, inevitably leads to eye damage. This is also true for red laser, among others in use on the underside of the mouse with light sensor.
For more information, see Optical radiation Optical Radiation in work situations - Practical aspects of implementation in the Netherlands of the EU Directive on exposure to artificial sources of optical radiation (expense Ministry of Social Affairs, found on the site www.rivm.nl ).
Measure and assess
Lighting intensity can be measured with an illuminance meter or lux meter and is measured in lux (lx = 1 lm / m 2). To measure correctly by illumination refers to NEN 1891. The recommended values are included in the BS EN 12464-1: 2011. The basis of a correct measurement of the illuminance is making a measurement grating. For a space generally applies a grid of 1 × 1 m. And for measuring the illuminance of a work surface 30 × 30 cm.
In addition to the measurement in the horizontal plane, the illumination shall also be measured in the vertical plane. Vertical illumination is of importance for the perception of the spatial dimensions and shapes, for sensing of obstacles and be able to see each other's face and to the interpersonal communication. Vertical illuminance is also important for public safety.
The luminance / brightness is to be measured with a luminance meter, and is expressed in candelas per square meter (cd / m 2). When measuring luminances / brightnesses goes to the next to the average value of the self-luminous or light-reflecting object mainly to the peak values and to determine the brightness ratios. Camera having a luminance different luminances can be brought in in the image area at one time.
For luminance ratios (L min: L max) generally applies to a maximum of 1:10 between stage (also the screen) and walls, surfaces of cabinets, tables, ceilings, cabinets and workspace between 1:30 (also display ) and window air and outside buildings. To adapt quietly from light to dark and dark to light, our eye works in log10 steps. A peaceful transition from 10 to 100 and from 100 to 1000 vv, processes view easier than abrupt transitions and great clarity.
measures
Jobs and direct accesses to belong during the presence of the workers to be illuminated sufficiently and effectively by daylight, artificial or both ( Art. 6.3 Conditions Decree ). It should also be kept out direct sunlight ( Art. 6.4 Conditions Decree ). Also have windows in areas where people work with computers, are equipped with adequate light resistance (Occupational Health and Safety
Regulations). use in spaces with monitors preferably twinrolscreens or twinplissés. With this daylight prevention may be achieved a brightness ratio of up to a factor of 30, while the environment outside still -they can be observed the limited-. A good side effect is that as the sun light barrier is provided with a metallized side also these cold and certainly many resulting heat radiation stops. Which is energy-saving.
normal lighting
The normal lighting in office and laboratory space must be horizontal at least 500 lux on the working plane and its 300 lux vertical (cylindrical) in space to observe to see each other and obstacles. For a natural color perception should be the color rendering index Ra> 80. The more complete the spectral distribution of the light is, the better is the color reproduction. Furthermore, the values of illumination and uniformity must at least comply with the requirements of BS EN12464-1.
Strengths lights above give 800 lux on the eye at 'normal' working conditions did not improve the performance efficiency. For office work in the workshop work (display and administration) is the minimum (standard) practice illuminance 500 lux on the worksheet. In places in the workplace where it is certain that there is not worked, the illuminance can be 40% lower. Illuminances of below 200 lux create a workspace unpleasant and have a negative effect on the performance and well-being (NEN 3087).
In places where one comes occasionally, for the orientation requires an illuminance of at least 10 lux. If need work at this place, it is necessary on the level of orientation lighting switch to the level of work lighting.
Lighting intensities above 800 lux (up to about 3000 lux) are especially suitable as a special working lights, for example, for precision work, such as color and quality, surgery or precision assembly. Here again, therefore, high color rendering factor.
Emergency lighting standard BS EN 1838 applies to sites can occur when light spot danger to persons such as rotating machinery, chemical reactions, or areas with a lot of people is a sound business and skilled emergency and / or anti-panic lighting is always a requirement.
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