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05-14-2012, 04:23 PM   #31
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This thread is getting rather physical! Lots of chest thumping.

I suggest we create a new sub forum titled Advanced Quantum Physics 404 for this thread and other similar ones.

05-14-2012, 04:28 PM   #32
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QuoteOriginally posted by Lowell Goudge Quote
the smaller the aperture you remove much more of the "perfect front" in proportion to the distorted front from the blades
I know which point you were trying to make. The problem is that you think you understand diffraction and only the explainations can be easier or more difficult to understand. Of course, it doesn't really matter. So, for the curious minds only ...

The front coming "from the blades" is not distorted, it is still part of the original perfect front. But there will be a missing part of the full front which has died.

Sometimes in Theoretical Physics field theories, there are mathematical theorems mapping a surface effect onto an edge effect (via boundary constraints of differential equations etc.). But even then, the more intuitive explainations are in terms of the original fields. Of course, you need some kind of device to remove parts of the original wavefront. But that could be an aspherical lens diverting parts of the wavefront off sensor. There would be no edge but still the full diffraction effect. Moreover, if you have an obstruction within the aperture, you have the same edges but almost no diffraction effect. Because you remove a less critical part of the original wavefront.

And to fully underline that diffraction is no edge effect at all... You can combine the signal from multiple lenses (all of them having apertures with full edge effects) into a combined signal with almost no diffraction loss. This is used in radio astronomy where sometimes hundreds of scopes are combined.

If you have trouble to understand this in terms of physics, you may think of it in an information theory way. The wavefront reaching the camera has full information, but the lens will only transmit a fraction of this information into the camera. This loss of information is what causes diffraction and noise. To call this an edge effect would be like calling a loss of information a property of the bits on the edges of a memory chip. While it obviously is a memory capacity effect.
05-14-2012, 04:43 PM   #33
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QuoteOriginally posted by selar Quote
This thread is getting rather physical! Lots of chest thumping.

I suggest we create a new sub forum titled Advanced Quantum Physics 404 for this thread and other similar ones.
There was no reason to extend this thread beyond post #3, incl. your post #6. I don't understand what chest thumping means in English. But I really only try to explain what diffraction is so that questions like the OP don't need be asked.

I think it is worth the effort to understand where diffraction really comes from, i.e., what the underlying cause is and that it is much more fundamental than an edge effect. Edges can be avoided, diffraction cannot. E.g., once you understand it you immediately see what's wrong with the light field idea (which tries to capture direction and position at the same time which as I already said causes a severe diffraction limitation).
05-14-2012, 06:15 PM   #34
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QuoteOriginally posted by falconeye Quote
There was no reason to extend this thread beyond post #3
One could easily also say that there was no reason to extend this beyond post 2. Needless pontification thereafter.

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