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An electromagnetic wave propagating along a path C has the phase shift over C as if it was propagating a path in a vacuum, length of which, is equal to the optical path length of C. Thus, if a wave is traveling through several different media, then the optical path length of each medium can be added to find the total optical path length. The ...
The optical path length from the light source is used to compute the phase. The derivative of the position of the ray in the focal region on the source position is used to obtain the width of the ray, and from that the amplitude of the plane wave. The result is the point spread function, whose Fourier transform is the optical transfer function.
Optical path (OP) is the trajectory that a light ray follows as it propagates through an optical medium. The geometrical optical-path length or simply geometrical path length ( GPD ) is the length of a segment in a given OP, i.e., the Euclidean distance integrated along a ray between any two points. [ 1 ]
The path length can be adjusted by changing the incidence angle Φ. Another category of multipass cells is generally referred to as circular multipass reflection cells. They were first introduced by Thoma and co-workers in 1994. [ 7 ]
A light ray enters a component crossing its input plane at a distance x 1 from the optical axis, traveling in a direction that makes an angle θ 1 with the optical axis. After propagation to the output plane that ray is found at a distance x 2 from the optical axis and at an angle θ 2 with respect to it.
Subscripts 1 and 2 refer to initial and final optical media respectively. These ratios are sometimes also used, following simply from other definitions of refractive index, wave phase velocity, and the luminal speed equation:
The air mass coefficient defines the direct optical path length through the Earth's atmosphere, expressed as a ratio relative to the path length vertically upwards, i.e. at the zenith. The air mass coefficient can be used to help characterize the solar spectrum after solar radiation has traveled through the atmosphere.
A slightly more rigorous definition of a light ray follows from Fermat's principle, which states that the path taken between two points by a ray of light is the path that can be traversed in the least time. [1] Geometrical optics is often simplified by making the paraxial approximation, or "small angle approximation".