Criteria for the determination of the thermal retinal image diameter

For a given power entering the eye, the level of retinal thermal hazard depends on the retinal image size over which that power is distributed. Maximum permissible exposure limits are given in terms of the angular subtense of the apparent Source a., which describes the diameter of the retinal image. Since this parameter scales the retinal thermal exposure limits (MPE), it is a direct measure of the relative thermal hazard of different retinal images, and thus should be seen as 'thermally effective' rather than 'optical' diameter of the retinal image. From the method given in IEC 60825-1 for the analysis of non-uniform Sources, a general method for the analysis of non-top hat profiles was derived and is Suggested as general analysis method for the angular subtense of the apparent Source for a given image. This and other criteria are compared with the results of thermal models.