Classification of extended source products according to IEC 60825-1

Since Edition 2 of IEC 60825-1, the classification of products such line lasers, scanners, DOE or others that produce an extended retinal image can be based either on a simplified analysis, assuming a small retinal image, or on an extended analysis, where the angular subtense of the apparent source needs to be characterized as well as the classification needs to be based on the “most restrictive position”. Even though this concept is standardized for almost 10 years, uncertainties in the application are frequent and discussion of the concept in the form of examples should be helpful. It is emphasized that in many cases, there is not “one” apparent source associated to a given product, and that further distances can be more restrictive than closer distances, which is not intuitively known from conventional sources and is the very reason for the special procedure defined in IEC 60825-1.