MICROSCOPY: Imaging a field of radiated light and it's source
I have a question about observing a field of radiated light (and it's source) through a microscope, specifically vis magnification and the scale of the final image observed (the field, and also the source).
I have a slice of field intensity at the plane of a microscope's numerical aperture (i.e. all light entering the appropriate half-cone angle of 20 degrees). It's an accurate map of the intensity — it looks as expected.
The objective is 75x, and the aperture sits about 1mm from a light source (a particle) with well-known dimensions.
WHAT I AM CONFUSED ABOUT:
Since the particle sits 1mm below the plane of the field I've calculated, how do I apply the 75x magnification to both the field and the particle to reform an image with appropriate dimensions (i.e. what I see when I look through the microscope)?
The most obvious approach to me is to take the objective's focal-length, and then ray trace the field and the particle independently to the same image observation-point. Then put them back together. But this isn't giving the result I expected (particle location/dimensions don't make sense relative to the field).
A reminder of the basic optics here would be highly appreciated, as this has me irritatingly confused.