Safety classification of line lasers as extended source

Line lasers are good examples to discuss the safety classification of a laser product as extended source according to IEC 60825-1. It is necessary to consider different accommodations of the eye, from accommodation to the beam waist in the diverging axis (the vertex of the line) to accommodation to infinity, which results in a retinal line image. Measurements and the classification analyses were performed for a common line laser. It was found that accommodation to the beam waist in the diverging axis produces the most critical retinal image and can be considered as “the apparent source.” Compared to the classification as a small source, classification as an extended source permits a factor of 5.8 higher power output. We argue that performing direct retinal image measurements with a CCD camera is more accurate and requires less effort than measuring beam parameters in the two axes and calculating the relevant parameters.