Photobiological Safety Testing of Image Projectors

Categories: Certification & Calibration, General & Specialty Lighting, Safety & Compliance Testing, Emission Spectrum

Based on the approach adopted by IEC 62471:2006, new emission limits and a revised retinal thermal hazard weighting function are derived from the ICNIRP 2013 guidelines for incoherent visible and infrared radiation [1], and a measurement distance of one metre from the closest point of human access is implemented. In the case of image projectors, this plane corresponds to that of the projection lens.

HazardHazard Weighting FunctionUnits
UV Skin and Anterior Eye, EsS(λ)W m-2
UVA Eye, EUVA-W m-2
Retinal Blue Light, EUVAB(λ)W m-2 sr-1
Retinal Blue Light Small Source, EBB(λ)W m-2
Retinal Thermal, LRR(λ)W m-2 sr-1
IR anterior eye, EIR-W m-2
*EN/ IEC 62471-5 hazards considered  

The emission of image projectors may be continuous wave or pulsed, depending on the source and image technology used. Pulsed emission is defined as that for which the peak radiated power exceeds the average radiant power by at least 1.5 times. For pulsed source, all but the retina thermal hazard are time averaged.

The apparent source of image projectors is the exit pupil, located behind the projection lens. The location and angular subtense of the exit pupil should be determined in evaluation of retinal hazards.

EN/ IEC 62471-5 spectral weighting functions
EN/ IEC 62471-5 spectral weighting functions
Image of projector exit pupil
Image of projector exit pupil

Projectors should be set up to worst case conditions (colour, brightness) and the throw ratio, defined as the distance from between exit pupil to screen to width of image, should be setup according to the projector optics type, fixed, zoomable or interchangeable lens.

Image projectors are classified according to degree of risk, from the no reasonably forseeable optical hazard RG0 to the hazardous for momentary exposure RG3. RG0 / RG1 projectors include conventional tungsten halogen slide or film projectors for home use or pico-projectors whilst RG2 projectors include home-use projectors. RG3 projectors are high power projectors used in cinemas or theatres and are not for household use.

Labelling requirements are provided for RG2 and RG3. In addition to labelling, RG2 and RG3 projectors should have a soft start feature to ensure full emission starts no sooner than one second after initial illumination to enable activation of the aversion response.  RG3 products should also be provided with hazard distance information to assist in installation restricted control areas and risk assessment 

References