Эротические рассказы

Optical Engineering Science. Stephen RoltЧитать онлайн книгу.

Optical Engineering Science - Stephen Rolt


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L, is defined as the shift in the axial image position for a unit shift in the object position, i.e.:

      (1.10)equation

equation

      And:

      (1.11)equation

      1.4.1 General

      The analysis presented thus far is entirely independent of the optical components that might populate the idealised optical system. In this section we will begin to consider, from the perspective of ray optics, the behaviour of real elements that make up this generalised system. At a basic level, only a few behaviours need to be considered in order to understand the propagation of rays through a real optical system. These are:

       Propagation through a homogeneous medium

       Refraction at a planar surface

       Refraction at a curved (spherical) surface

       Refraction through lenses

       Reflection at a planar surface

       Reflection at a curved (spherical) surface

      As previously set out, the path of rays through a system is governed entirely by Fermat's principle. From this point, we will apply the simplest definition of Fermat's principle and assume that the time or optical path of rays is minimised. As far as propagation through a homogeneous medium is concerned, this leads to a perhaps obvious and trivial conclusion that light travels in straight lines. In fact, this describes a specific application of Fermat's principal, known as Hero's principle, namely that light follows the path of minimum distance between two points within a homogeneous medium.

      1.4.2 Refraction at a Plane Surface and Snell's Law

      The law governing refraction at a planar surface is universally attributed to Willebrord Snellius and referred to as Snell's law. This states that both incident and refracted rays lie in the same plane and their angles of incidence and refraction (with respect to surface normal) are given by:

      (1.12)equation

      The refractive indices of some optical materials (at 550 nm) are listed below:

       Glass (BK7): 1.52

       Plastic (Acrylic): 1.48

       Water: 1.33

       Air: 1.00027

Illustration of refraction at a plane surface.

      A single refractive surface is an example of an afocal system, where both focal lengths are infinite. Although it does not bring a parallel beam of light to a focus, it does form an image that is a geometrically true representation of the object.

      1.4.3 Refraction at a Curved (Spherical) Surface

      As before, the special case of refraction at a spherical surface may be described by Snell's law:

equation Geometrical illustration of refraction at a spherical surface. equation

      Hence:

equation

      We can finally calculate φ in terms of θ:

      Equation (1.14) can be used to trace any ray that is


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