I am attempting to measure, in accordance with IEC 60825-1+A1 +A2, the size of the apparent source of a LED plastic fiber optic driver when the fiber is removed. The driver assembly consists of a visible red LED, clear magnifying lens and a barrel into which the 2.2 mm dia plastic fiber cable is inserted up to the lens surface. When I focus a relay lens near the tip of the barrel, I can find a minimal size image that consists of a bright center with concentric rings (reflections along the length of the barrel). The image diameter is about 2.3 mm. When I focus further inside the assembly, I can find a smaller virtual image of the magnified LED surface - about 1 mm diameter. Which of these two images is considered to be the apparent source?
If the image near the tip of the barrel is the apparent source, it is a near circular image and I can use a circular aperture to determine the apparent size. If the apparent source is the one inside the barrel, the image is square (the LED die), and the standard appears to say that I must use a rectangular aperture. Is this correct or may I use a circular aperture? If so, the standard does not provide the procedure to determine the apparent size using a rectangular aperture. Any hints? Richard Woods Sensormatic Electronics Tyco International This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
