Unlike infrared sources, blue and violet diodes (400–450 nm) emit light within the visible spectrum; therefore, adjustment glasses compliant with standard EN 208 can be used with them. These special filters do not block the beam completely, but selectively allow part of it to pass through, thereby reducing its power to a safe level corresponding to Class 2 (max. 1 mW). They thus enable safe and accurate visual inspection during the alignment of optical paths without the risk of damage to the retina.