Light hazard


Optical radiation, especially in the ultraviolet region, is potentially hazardous to skin and eyes. Gigahertz-Optik GmbH produces optical radiation measuring devices to determine the UV radiation (skin and eye), blue light (eye) and infrared (skin) hazards in accordance with international standards. Some typical application examples of Gigahertz-Optik GmbH products are listed in this chapter.

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App. 009

Assessment of blue light hazard from artificial light sources

The potential effects of the blue light content within display devices and lighting has been a subject of particular interest and concern, particularly since the widespread introduction of solid-state lighting.  ‘Blue light hazard’ refers to a specific photobiological hazard concerned with the possibility of photochemical-induced damage to the retina within the eye (photoretinitis). It is not concerned with the possible disruption to circadian rhythms, for example (see Human Centric Lighting application).

Only radiation that passes through the cornea of the eye and is imaged on the retina is relevant for blue light hazard assessment. Understanding the appropriate standards and the necessary measurement techniques can appear somewhat daunting at first. 

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ICNIRP guidelines [1] form the basis of non-coherent optical radiation exposure limits in most standards and regulations. The blue light hazard function is actually defined over the 300nm - 700nm wavelength range, but with a strong responsivity peak in the blue region. Hence, high power phosphor conversion LEDs with their relatively intense blue emission peak compared to other lighting technologies, have been a particular concern.

blue light hazard 02

The size of the pupil defines the solid angle over which the eye projects an image onto the retina.

Therefore, the brightness (luminance) of the source is the important criteria for determining the irradiance level on the retina. Standards specify limits for blue light exposure in terms of radiance (Wm-2sr-1) within defined field of views and weighted by the blue light hazard function. Due to the natural rapid movement of the eye (saccades), the retinal irradiance decreases with time, a fact that is incorporated within the relevant standards.

Lighting products manufactured within and imported into Europe must conform to the Low Voltage Directive (LVD) 2014/35/EU in order to be CE marked.  For luminaires this requires compliance with EN 60598-1 [2],the general requirements standard for luminaires, which includes photobiological safety testing. Since 2006 photobiological safety testing of lamps and lighting products has been addressed by the horizontal standard IEC 62471 [3]which includes six hazard functions over the 200-3000nm wavelength range. However, for most general lighting products such comprehensive testing is unnecessarily onerous and hence IEC TR 62778 [4] is referenced in vertical product standards for the assessment of retinal blue light hazard.  Within IEC TR 62778 an assessment is made whether a luminaire exceeds the limits of IEC 62471 risk group 1 (RG1) at a distance of 200mm. Sources with luminance of <10000 cd/m2 are RG0 and require no further testing. Blue light weighted radiance needs to be measured in an 11mrad FOV for sources of size >=2.2mm whereas smaller sources only require irradiance measurement. The X1-3 Optometer in conjunction with the XD-45-HB blue light hazard detector facilitates these measurement requirements of IEC TR 62778.

For products not covered under the LVD, the prevention of blue light hazard remains a legal requirement under the General Product Safety Directive (GPSD) 2001/95/EC.

Blue light hazard assessment is also a requirement within health and safety at work legislation. The EU artificial optical radiation directive (AORD) [5], imposes limits on worker exposure to non-laser sources of optical radiation. The AORD exposure limits are consistent with those of EN 62471 [6].


[1] International Commission on Non-Ionizing Radiation Protection Guidelines

[2] EN 60598-1:2015 Luminaires – Part 1: General requirements and tests 

[3] IEC 62471:2006 Photobiological safety of lamps and lamp systems

[4] TR 62778:2014 Application of IEC 62471 for the assessment of blue light hazard to light sources and luminaires

[5] Directive 2006/25/EC – artificial optical radiation

[6] EN 62471:2008 Photobiological safety of lamps and lamp systems

App. 010

Measurement of non-laser optical radiation safety at work

The European Directive 2006/25/EC [1] lays down minimum requirements for the protection of the health and safety of workers from the risks related to artificial optical radiation. It is implemented in law by all member states and covers exposure of skin and eyes to ultraviolet, visible and infrared (to 3000nm) radiation, both from coherent (laser) and non-coherent (non-laser) light sources. The exposure limit values in the directive are based on the work of the International Commission on Non-Ionizing Radiation Protection (ICNIRP) [2]. 

The methodology for determining exposure levels to laser radiation follows the well-established IEC 60825 [3] standard whereas for non-laser radiation the CIE/CEN standards in the form of EN 62471:2008 [4] is applicable.

Hazards relating to skin and the front surface of the eye require the measurement of irradiance whereas hazards to the eye itself require the measurement of radiance. EN 62471:2008 considers the following six hazards with respect to exposure over a period of up to eight hours:

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Wavelength range

Eye Skin
Actinic UV 200 – 400nm (*)

Cornea – photokeratitis

Lens – cataractogenisis

Conjunctiva – conjunctivitis

Erythema Elastosis
Near UV 315 – 400nm Lens – cataractogenisis  
Blue light 300 – 700nm (*) Retina – photoretinitis  
Retinal thermal 380 – 1400nm (*) Retina – retinal burn  
IR radiation eye 780 – 3000nm Cornea – cornea burn  
Thermal skin 380 – 3000nm   Skin burn
(*) Action spectra weighting applied

Photobiological hazards considered in IEC EN 62471 and EU Directive 2006/25/EC


It should be noted that there are some minor differences between EN 62471:2008 and the limits in IEC 62471:2006 [5] with respect to blue light small source and retinal thermal weak stimulus limits that result from revisions in ICNIRP guidelines.

The X1-3 Optometer facilitates the measurement of all UV and blue light hazards within the scope of EN 62471. The XD-45-HUV hazard detector measures actinic UV and near UV irradiances and the XD-45-HB blue light hazard detector measures blue light weighted radiance within the required fields of view.


[1] Directive 2006/25/EC - artificial optical radiation 

[2] International Commission on Non-Ionizing Radiation Protection Guidelines

[3] IEC 60825-1:2014 Safety of laser products - Part 1: Equipment classification and requirements

[4] EN 62471:2008 Photobiological safety of lamps and lamp systems

[5] IEC 62471:2006 Photobiological safety of lamps and lamp systems

[6] EN 14255 Parts 1 and 2: Measurement and assessment of personal exposures to incoherent optical radiation

App. 011

Erythema-effective irradiance measurement of sun tanning studios

Concerns over the safety of both commercial and home use sun tanning lamps led to the EU’s Scientific Committee on Consumer Products (SCCP) [1] recommending a limit of 0.3W/m2 erythema effective irradiance for all cosmetic use sun tanning lamps. This level is implemented within legally binding European regulations for both manufacturers and operators. Erythema is the reddening of the skin which is an inflammatory response caused by, for example, the actinic effect of exposure to UV radiation.  Erythemal effective irradiance (CIE S 007-1998) [2] is measured over the wavelength range 250nm to 400nm.

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Within Europe, sun tanning products must conform to the Low Voltage Directive (LVD) 2014/35/EU in order to be CE marked which requires type-testing against EN 60335-2-27- 2010 [3]. A high quality UV spectroradiometer such as the BTS2048-UV-S is required to measure the spectral irradiance of appliances, from which erythema effective irradiance is determined over UV-A and UV-B wavelength regions 250-320nm (UV-B) and 320-400nm (UV-A). Note that these UV ranges differ from standard CIE  UV-A (315-400nm) and UV-B (280-315nm) wavelength ranges. The total UV-A plus UV-B effective irradiance must not be in excess of 0.3 W.m-2. Additionally, the un-weighted irradiance 250-280nm must not exceed 0.003 W.m-2. Excellent scattered light rejection is required of the spectroradiometer otherwise products may unnecessarily fail this criterion. The appliance type is then determined using the following table: 

UV Appliance Type

250 < λ <320nm

ery-eff irradiance W/m2

320nm < λ <400 nm

ery-eff irradiance W/m2
1 < 0,0005 > 0,15 Professional use under supervision of appropriately trained persons.
2 0,0005 to 0,15 > 0,15 Professional use under supervision of appropriately trained persons.
3 < 0,15 < 0,15 Suitable for household use without training.
4 > 0,15 < 0,15 Intended to be used following medical advice.


Routine inspection and compliance checking by either the sun tanning studio operator or by local authority inspectors is more conveniently performed with a suitable UV radiometer such as the X1-4 meter. The XD-45-ERYC multi-detector based sensor supplied with the X1-4 meter also incorporates a UV-C irradiance detector for maximum safety compliance testing.


[1] SCCP Biological effects of ultraviolet radiation relevant to health with particular reference to sun beds for cosmetic purposes

[2] CIE S 007-1998 Erythema Reference Action Spectrum and Standard Erythema Dose 

[3] EN 60335-2-27:2013 Household and similar electrical appliances. Safety. Particular requirements for appliances for skin exposure to ultraviolet and infrared radiation

App. 012

Measurement of actinic and safety-related irradiance of UV-C air disinfection

Shortwave UV-C radiation is highly bactericidal because it is absorbed by the DNA of microorganisms which destroys its structure. Referred to as ultraviolet germicidal irradiation (UVGI), UV-C wavelengths around 260-270nm are most effective in combating airborne bacteria, viruses and other microorganisms such as mildews and yeasts. Disinfecting the air can prevent the transmission of a variety of airborne infections such as tuberculosis and pandemic influenza. It can also prevent contamination of raw materials and food. Therefore, UV-C air disinfection systems are being increasingly used within healthcare environments, public places, industry, and research facilities.

Manufacturers need to optimise the efficacy of the UV germicidal action of air purification systems whilst ensuring no hazard is presented to occupants. 

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The specialist UV-C detector UV-3725 is designed to withstand the high-energy UV radiation present within air disinfection systems whilst offering the dynamic range to enable low level hazard measurements. To measure the irradiance of such extended sources, radiometers must be designed with a cosine field of view function. The required cosine-correction optics and photodetector components must also be pre-aged because of the high-energy UV radiation. Occupant safety [1] must be ensured for rooms fitted with ceiling-mounted air disinfection systems. The monitoring of exposure to UV-C [2] of long term occupants (e.g. healthcare workers [3]) within rooms fitted with air purification can be achieved with the use of personal dosimeters such as the X2000.


[1] S Milonova et al, Occupant UV Exposure Measurements for Upper-Room Ultraviolet Germicidal Irradiation

[2] MW First et al, Monitoring Human Exposures to Upper-Room Germicidal Ultraviolet Irradiation

[3] UV-C Exposure and Health Effects in Surgical Suite Personnel

App. 013

Personal dosimetry of UV erythema effective radiation exposure

The assessment of erythema-effective radiation exposure is usually based on data recorded by stationary measuring devices, but this does not replicate the actual exposure experienced in most real situations. The measurement of UV irradiation experienced by outdoor workers, for example, requires personal dosimeters – see references [1]–[8].  Outdoor sports players may also be subjected to relatively high doses of UV [9].

Because of the different activities of the selected target groups, the solar irradiance levels experienced are changing continually throughout the day.  Therefore, suitable dosimeters must provide data logging with high measurement rates and large data storage capacity. With the X2012 as the successor to the X2000 data logger, Gigahertz-Optik GmbH demonstrates its expertise as a project partner for custom research projects in optical radiation measurement technology.

App. 014

Measurement and evaluation of UV radiation during arc welding

The use of personal protection equipment (PPE) is essential during welding processes due to the high levels of UV radiation produced. Evaluating the hazard associated with UV exposure during welding processes, requires the spectral irradiance to be measured and weighted in terms of biological effectiveness. The measurement of the dynamic optical processes within welding arcs requires specialist equipment as well as expertise in its use and evaluation of the measurement results.  The IFA, Sankt Augustin and the Federal Institute for Occupational Safety and Health, Dortmund have produced comprehensive research reportson the measurement and evaluation of UV radiation exposure during welding processes [1], including consideration of the dynamic aspects [2] . The reports employ a wide range of specialist measurement equipment from Gigahertz-Optik GmbH, including UV spectroradiometers [3], UV radiometers [4][5] and personal dosimeters [6][7].

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[1] IFA – Emission of UV radiation during arc welding

[2] Optische Strahlenbelastung beim Schweißen – Erfassung und Bewertung

[3] BTS2048-UV-S for high quality UV measurements

[4] P-9801 with XD45-HUV and XD-45-HB, fast 8-channel Optometer with ICNIRP UV and Blue light hazard detectors

[5] P-9710 Optometer with LDM-9811 radiance detector with 1,7 mrad for LB

[6] X2012-11 Data logger Dosimeter for ICNIRP actinic UV irradiance

[7] X2012-14 Data logger Dosimeter for radiometric UV-A und UV-B irradiance