09-03-2010, 08:52 PM
(This post was last modified: 09-03-2010, 09:08 PM by Brightcolours.)
[quote name='wim' timestamp='1283544989' post='2473']
Your drawing is actually incorrect. The light should be refracted, twice (once at each mirror surface, see for example [url="http://www.thorlabs.de/NewGroupPage9.cfm?ObjectGroup_ID=915"]http://www.thorlabs....ectGroup_ID=915[/url]), therefore only causing at worst two images slightly offset to each other, as the beams before and after the mirror have to be parallel. Also, the scenario as you draw it here with more than one reflection is not possible, unless they had chosen the refractive index of the reflective mirror glass deliberately so to create those reflections (IOW, a very, very high refractive index). And good coatings will reduce these reflections by 99.8 % or more.
I therefore conclude, that final proof for the cause of the reflections in those images, unless scientifically proven to be from the mirror, may well be something different. They could well be reflections of the sensor, re-reflected by the AA-filter, or even a similar thing as the black dot phenomenon, IOW, a processing problem when reading the raw data. Or something completely different for that matter, but very likely not any reflections caused by the mirror, unless they really made a terrible engineering error.
Kind regards, Wim
[/quote]
My drawing is very correct. No idea why you think otherwise. The 3rd (2nd ghost image) I only put in to show that in theory that can happen (but obviously, you won't see it as the light intensity would be very low by then), just disregard that 3rd image.
The diagram from thorlabs shows something different. They show the problem of getting ghost measurements from the part of light they are splitting off the main beam, in the A55's case the light that would be going to the AF sensor.
They have NO diagram that shows what happens to the image itself. But MY diagram does show that. Just a fact of 45 degrees slabs of glass.
Anyway, whether or not you want to believe it or not, the cause of the ghost lights is evident, and it is in the use of that mirror. Not something I dreamt up, Wim.
And also the reason why others either used a pellicle instead of a glass mirror, or a prism assembly.
And yes, even the Thor diagram does show how the 2 reflective surfaces are problematic.
That I did not draw in unknown diffraction should be forgiven, as it is not important to make what is going on clear.
But anyway, if we take an unknown refraction index into account, things might look like this:
![[Image: FEE29AE6B9F14C1DA838E64295E7AD2F.jpg]](http://g1.img-dpreview.com/FEE29AE6B9F14C1DA838E64295E7AD2F.jpg)
Your drawing is actually incorrect. The light should be refracted, twice (once at each mirror surface, see for example [url="http://www.thorlabs.de/NewGroupPage9.cfm?ObjectGroup_ID=915"]http://www.thorlabs....ectGroup_ID=915[/url]), therefore only causing at worst two images slightly offset to each other, as the beams before and after the mirror have to be parallel. Also, the scenario as you draw it here with more than one reflection is not possible, unless they had chosen the refractive index of the reflective mirror glass deliberately so to create those reflections (IOW, a very, very high refractive index). And good coatings will reduce these reflections by 99.8 % or more.
I therefore conclude, that final proof for the cause of the reflections in those images, unless scientifically proven to be from the mirror, may well be something different. They could well be reflections of the sensor, re-reflected by the AA-filter, or even a similar thing as the black dot phenomenon, IOW, a processing problem when reading the raw data. Or something completely different for that matter, but very likely not any reflections caused by the mirror, unless they really made a terrible engineering error.
Kind regards, Wim
[/quote]
My drawing is very correct. No idea why you think otherwise. The 3rd (2nd ghost image) I only put in to show that in theory that can happen (but obviously, you won't see it as the light intensity would be very low by then), just disregard that 3rd image.
The diagram from thorlabs shows something different. They show the problem of getting ghost measurements from the part of light they are splitting off the main beam, in the A55's case the light that would be going to the AF sensor.
They have NO diagram that shows what happens to the image itself. But MY diagram does show that. Just a fact of 45 degrees slabs of glass.
Anyway, whether or not you want to believe it or not, the cause of the ghost lights is evident, and it is in the use of that mirror. Not something I dreamt up, Wim.
And also the reason why others either used a pellicle instead of a glass mirror, or a prism assembly.
And yes, even the Thor diagram does show how the 2 reflective surfaces are problematic.
That I did not draw in unknown diffraction should be forgiven, as it is not important to make what is going on clear.
But anyway, if we take an unknown refraction index into account, things might look like this: