If we assume that a normal eye observes the image through the eyepiece, the eyepiece must project a distant image from the real image produced by the objective.
For example, the real image may be recorded on a photographic plate; it may be measured; it can be physically altered by polarization, by spectrum analysis of the light employed by absorbing layers, &c. The greatest advantage of the compound microscope is that it represents a larger area, and this much more completely than is possible in the simple form.
But as the object-side focus F2 lies behind the eyepiece, the real image is not produced, but the converging pencils from the objective are changed by the eyepiece into parallels; and the point 0 1 in the top of the object y appears at the top to the eye, i.e.
The pencils producing the real image are very much more acute, and their inclination is the smaller the stronger the magnification.
The eyepiece, which by means of narrow pencils represents the relatively large real image at infinity, transmits from all points of this real image parallel pencils, whereby the inclination of the principal rays becomes further increased.