Hi Kevin,

For this kind of exercise, I would use the Float By Stop Size aperture definition, and if you want to make a forward model, you might be required to enable ray-aiming.

Under this aperture definition, you can fix your STOP semi-diameter and OpticStudio will fill it. How do you know the aperture size? If you know the objective lens manufacturer, you can deduce the focal length of their tube lens. The most popular ones are 200 mm for Nikon, Leica, Mitutoyo, and Thorlabs, 180 mm for Olympus, and 164.5 mm for Zeiss. Since you have the magnification (10X), and the magnification is the ratio between the tube lens and objective lens focal length, you can deduce your objective lens focal length. For example, if you have a Nikon objective, your objective focal length is 200 / 10 = 10 mm. Then, the NA is the sine of half the acceptance angle, which is calculated as atan( semi-diameter / focal length ). Therefore semi-diameter = tan( asin( NA ) ) * focal length = 2.582 mm.

As for your other issue, you seem to have fixed the semi-diameter of your lenses, therefore it puts an aperture on them (you can read (aper) in the left column) and if the rays don’t pass through the aperture, they are terminated.

Let me know if this helps, and take care,

David

Also, use Cosine-Cubed Apodization of the pupil to include the non-uniform pupil illumination produced by a point source irradiating a close pupil.

• M