使用無限校正物鏡和管鏡

In order to create an image with an infinity-corrected objective, a tube lens must be used to focus the image. One advantage to using an infinity-corrected objective with a tube lens is that there can be a space between the objective and tube lens. The space allows additional optical components to be inserted into the system, such as optical filters or beamsplitters. The distance between an infinity-corrected objective and the tube lens (L) can be varied from the recommended or optimal, but this will affect the image field diameter ($ \varnothing $). Equations 1 and 2 are approximation formulas to determine the relation between ($ \varnothing $) and L.

(1)$$ \varnothing_1 =2 \times f_1 \times \text{NA} $$

(1)

$$ \varnothing_1 =2 \times f_1 \times \text{NA} $$

where $ \small{\varnothing _1} $ is exit pupil of the objective, $ \small{f_1} $ is focal length of the objective, and NA is the numerical aperture of the objective.

(2)$$ L = \frac{ \left( \varnothing_2 - \varnothing_1 \right) \times f_2 }{\varnothing} $$

(2)

$$ L = \frac{ \left( \varnothing_2 - \varnothing_1 \right) \times f_2 }{\varnothing} $$

Where L is the distance between the objective and the tube lens, $ \small{\varnothing _2} $ is entrance pupil of the tube lens, $ \small{f_2} $ is focal length of the tube lens, and $ \small{\varnothing } $ is the image field diameter.