Exit pupil, lens

The MTF curve can be described mathematically in terms of the above variables. As an example, the MTF [(7/( /)l of a lens employing incoherent illumination and a circular exit pupil is given by... 

Ophthalmic imagers often use a scanning technique with the pupil of the eye placed in the exit pupil of the scanning system [461]. This reduces image distortion and blurring due to the poor optical quality of the lens of the eye. Moreover, confocal detection can be used to suppress reflection, scattering, and fluorescence signals from the lens of the eye. 

Close the aperture diaphragm on the substage condenser so that its radius is 70-80% of the illuminated field (the exit pupil of the objective). Streening off the outer 20-30% of the exit pupil gives an approximate match between the NAs of condenser lens and objective lens. 

We now consider the relation between the wave function in the object plane and in the image plane z = Zi conjugate to this, in which h(z) vanishes h(zi) = 0. It is convenient to calculate this in two stages, first relating irixi, yu Zi) to the wave function in the exit pupil plane of the lens, f Xo, ya, Za) and then calculating the latter with the aid of Eq. (62). Introducing the paraxial solutions G(z), H z) such that... 

In the paraxial approximation, the aperture function A is simply a mathematical device defining the area of integration in the aperture plane A = 1 inside the pupil and A = 0 outside the pupil. If we wish to include the effect of geometric aberrations, however, we can represent them as a phase shift of the electron wave function at the exit pupil. Thus, if the lens suffers from spherical aberration, we write... 

F-number The ratio of the focal length of a lens to the diameter of the exit pupil of that lens. The F-number of a well-corrected lens is the reciprocal of twice its numerical aperture. 

If the telescope is to have a sizable field of view, as measured by the angle a, then the eyepiece could become prohibitively large. To reduce the diameter of the eyepiece, sl field lens is installed near the secondary focal plane of the objective. The field lens, which may be part of the eyepiece, directs the principal ray toward the axis and allows the diameter of the eyepiece to be reduced. Typically, the focal length of the field lens may be chosen so that the principal ray intersects the eyepiece at its periphery. This shifts the location of the exit pupil somewhat toward the eyepiece and slightly reduces the eye relief ht-tween the eye and the eyepiece. When the field lens is built into the eyepiece, the second lens in the eyepiece is called the eye lens. 

Figure 14 Graph illustrating the variation in refractive depth of a ray as a function of the starting position of the ray within the exit pupil of the lens. The graph is plotted for lenses with a range of numerical apertures.

After the transport of aqueous humor into the posterior chamber, it flows through the pupil into the anterior chamber where it provides oxygen and nutrition to the avascular lens and cornea. Aqueous humor then exits the anterior chamber through the trabecular meshwork and drains into Schlemm s canal which drains aqueous humor into the episcleral venous system. 

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