Screenshot above comes from page 6 of this datasheet
That's for OSRAM PLPT5 450KA blue laser diode.
So far I did not have any problems understanding technical drawings, so I suspect this may be a standard notation I've somehow never seen so far, or a custom notation used on laser diode (or other optical elements) datasheets, so it seemed natural to ask here first, some of you probably have already seen this on other datasheets..
The thing I don't understand is the part marked with red line: "⊕ 0.17 A", data apparenly meant for "Emission Point" location. At first I thought it's its radius/diameter, but the same drawing in other places uses typical ø symbol for that, so it's not diameter.
I also do see another "A", I think it's using the same font, but I don't see any correlation between those.
Please solve that mystery for me, I have a feeling that this is something basic, but it eludes me:
- red line, what does ⊕ symbol mean?
- red line, what does 0.17 dimension mean, and what is its unit ('A'? ampere?? angstrem??)
- red line, what does A mean here? (any relations to 'A' from green line?)
- green line, what is that black triangle denoted by [A] label?
it seems to be some marking/symbol, as it doesn't seem to be drawn in any way on the other two projections
Best Answer
This is Geometric Dimensioning and Tolerancing (aka GD&T). It is a newer and more specific way of dimensioning drawings compared to the traditional way of using dimensions everywhere. It came out of the UK weapons industry during and shortly after WW2, and is quite popular in industries where precise and clearly defined tolerances are important.
I'm not exactly fluent, but if I'm reading them correctly:
So the emission point is within 0.17mm of the axis defined by the cylindrical surface marked A.