Achromatic Lens - Design

Design

The first-order design of an achromat involves choosing the overall power of the doublet and the two glasses to use. The choice of glass gives the mean refractive index, often written as (for the refractive index at the Fraunhofer "d" spectral line wavelength), and the Abbe number (for the reciprocal of the glass dispersion). To make the linear dispersion of the system zero, the system must satisfy the equations

where the lens power is for a lens with focal length . Solving these two equations for and gives

Since, and the Abbe numbers are positive-valued, the power of the second element in the doublet is negative when the first element is positive.

Read more about this topic:  Achromatic Lens

Famous quotes containing the word design:

    Teaching is the perpetual end and office of all things. Teaching, instruction is the main design that shines through the sky and earth.
    Ralph Waldo Emerson (1803–1882)

    If I knew for a certainty that a man was coming to my house with the conscious design of doing me good, I should run for my life ... for fear that I should get some of his good done to me,—some of its virus mingled with my blood.
    Henry David Thoreau (1817–1862)

    For I choose that my remembrances of him should be pleasing, affecting, religious. I will love him as a glorified friend, after the free way of friendship, and not pay him a stiff sign of respect, as men do to those whom they fear. A passage read from his discourses, a moving provocation to works like his, any act or meeting which tends to awaken a pure thought, a flow of love, an original design of virtue, I call a worthy, a true commemoration.
    Ralph Waldo Emerson (1803–1882)