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Degeneration
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Hello all,
I've got an optics problem that I'm having some difficulty with, where I want to send a beam through a converging lens to obtain a certain image size. My incident profile is that of a ring with a certain thickness and use I use this as my object. I want an image of a certain size, so I've been using the thin lens equation to determine the lens' properties (magnification, focal length) - but I don't know if this is valid. The object has a significant ratio of the ring's (full width half max)/(ring radius), and when it is magnified through the lens, I want this ratio to remain the same.
Here is the issue: this ring-shaped laser beam (using an axicon to produce this shape) is collimated like http://www.wavelength-tech.com/images/axicon01.gif, and when I run simulations it turns out that this ratio of FWHM/Rad is NOT retained in the image. Is this use of the thin lens equation incorrect? I suspect it is because different parts of the ring are treated differently, i.e. the ring itself is treated as an uncollimated point source when passing through the lens, while the width of the ring is a collimated beam. Could anyone offer any insight? Perhaps a better way to compute the FWHM and radius of the ring passing through a converging lens with given parameters?
Many thanks
P.S. Here is the image linked to in case the hyperlink doesn't show: http://www.wavelength-tech.com/images/axicon01.gif
I've got an optics problem that I'm having some difficulty with, where I want to send a beam through a converging lens to obtain a certain image size. My incident profile is that of a ring with a certain thickness and use I use this as my object. I want an image of a certain size, so I've been using the thin lens equation to determine the lens' properties (magnification, focal length) - but I don't know if this is valid. The object has a significant ratio of the ring's (full width half max)/(ring radius), and when it is magnified through the lens, I want this ratio to remain the same.
Here is the issue: this ring-shaped laser beam (using an axicon to produce this shape) is collimated like http://www.wavelength-tech.com/images/axicon01.gif, and when I run simulations it turns out that this ratio of FWHM/Rad is NOT retained in the image. Is this use of the thin lens equation incorrect? I suspect it is because different parts of the ring are treated differently, i.e. the ring itself is treated as an uncollimated point source when passing through the lens, while the width of the ring is a collimated beam. Could anyone offer any insight? Perhaps a better way to compute the FWHM and radius of the ring passing through a converging lens with given parameters?
Many thanks
P.S. Here is the image linked to in case the hyperlink doesn't show: http://www.wavelength-tech.com/images/axicon01.gif
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