Complex Sources

We are specialised in analysing complex problems that arise in the application of standards and limits. Some examples:

  • There are several limits that have to be taken into consideration concurrently, e.g. for thermal and photochemical retinal damage.
  • The limits depend on the duration of the pulse, the pulse pattern, the overall duration of the exposure, the wavelength and on the diameter of the laser spot on tissue (on the retina). 
  • These dependencies are also partially correlated with each other, e.g. the influence of the pulse duration changes according to the wavelength. In the 2013 standard revision the influence of the spot size for thermal retinal damage will change according to the pulse duration (this dependency is a result of our research work).
  • The hazard depends on the optical imaging on the retina and thus on the accommodation condition of the eye and on the distance to the source.
  • The hazard changes in a complex way with the distance to the source, because the power that enters the eye changes as well as the optical imaging on the retina (we have carried out simulations of this in a research project by means of beam propagation calculation and on the basis of the results, extended sources have to be classified on the most restrictive position since the publication of the second edition of the IEC 60825-1 standard.
  • Scanned exposure of the retina can result from scanned sources – in such cases the standard cannot provide any satisfactory evaluation methods at present.
  • Sources can be ”combined“, e.g. several wavelengths or laser sources combined with LEDs. The corresponding bio-effects have to be taken into consideration for a risk analysis.
  • There are no satisfactory evaluation methods within the standard for irregular pulse sequences at present.
  • For some products it is necessary to take into consideration the restrictions of the applicability of the limits - for example during medical use.
  • The requirements of the technical standards, e.g. of IEC 60825-1 are not sufficient for specific products, respectively an adequate specific standard does yet not exist. In this case the product has to be designed according to the applicable legal requirements for a safe product. 

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