The answer to my questions can be found in Clause 5.2.2.4 of TR 60825-9. A rectangular aperture is required for oblong sources and the method of measurement is presented in that clause - it isn't easy. Sigh.
> -----Original Message----- > From: WOODS, RICHARD > Sent: Wednesday, June 11, 2003 9:50 AM > To: 'emc-pstc' > Subject: LED Emissions > > 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
