Читать книгу Optical Engineering Science - Stephen Rolt - Страница 15

We consider an ideal optical system which consists of a point source of light, the object, and an optical system that collects the light and re-directs all rays emanating from this point source or object, such that the rays converge onto a single point, the image point. At this stage, the interior workings of the optical system are undefined; the system behaves as a ‘black box’. The object is said to be located in object space and the image in image space and the pair of points are said to be conjugate points. This is illustrated in Figure 1.5.

In Figure 1.5, the two points P₁ and P₂ are conjugate. The optical system can be simple, for example a single lens, or it can be complex, containing many optical elements. The description above is entirely generalised. Where the object point lies on the optical axis, its image or conjugate point also lies on the optical axis. In Figure 1.5, the object point has a height of h₁ with respect to the optical axis and its corresponding image point has a height of h₂ with respect to the same axis. The ratio of these two heights gives the system (transverse) magnification, M:

(1.5)

Points occupying a plane perpendicular to the optical axis are conjugate to points lying on another plane perpendicular to the optical axis. These planes are known as conjugate planes.