# principal plane

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## prin·ci·pal plane

the theoretic plane of a compound lens system. See: principal point.

## ray

In geometrical optics, a straight line representing the direction of propagation of light.
axial ray A ray that is coincident with the axis of an optical system.
chief ray A ray joining an object point to the centre of the entrance pupil of an optical system (Fig. R2). See pencil of light.
emergent ray A ray of light in image space either after reflection (reflected ray) or after refraction (refracted ray).
extraordinary ray See birefringence.
incident ray A ray of light in object space that strikes a reflecting or refracting surface.
marginal ray A ray joining the axial point of an object to the edge or margin of an aperture or pupil (Fig. R2).
ordinary ray See birefringence.
paraxial ray A light ray that forms an angle of incidence so small that its value in radians is almost equal to its sine or its tangent. (i.e. sin θ = θ or tan θ = θ. These are approximate expressions referred to as the paraxial approximation (or the gaussian approximation). See paraxial optics; paraxial region; gaussian theory.
principal ray A ray joining the extreme off-axis object point to the centre of the entrance pupil or aperture (Fig. R2).
ray tracing Technique used in optical computation consisting of tracing the paths of light rays through an optical system by graphical methods or by using formulae. Nowadays, computer methods are used. See sign convention.
Fig. R2 Rays of light incident to the eye (E, centre of the entrance pupil of the eye)

 Table R1 Differences between the sine and the tangent values of various angles (in degrees and radians). The error is calculated between the sine value and the value in radians and between the value in radians and the tangent value angle (deg) angle (rad) sinevalue tangent value error (%) sine error error (%) tangent error 0.5 0.008 727 0.008 727 0.008 727 0.00 0.00 1 0.017 453 0.017 452 0.017 455 0.01 0.01 2 0.034 907 0.034 899 0.034 921 0.02 0.04 3 0.052 360 0.052 336 0.052 408 0.05 0.09 4 0.069 813 0.069 756 0.069 927 0.08 0.16 5 0.087 266 0.087 156 0.087 489 0.13 0.25 6 0.104 720 0.104 528 0.105 104 0.18 0.37 7 0.122 173 0.121 869 0.122 785 0.25 0.50 8 0.139 626 0.139 173 0.140 541 0.33 0.65 10 0.174 533 0.173 648 0.176 327 0.51 1.03 15 0.261 799 0.258 819 0.267 949 1.15 2.35 520 0.349 066 0.342 020 0.363 970 2.06 4.27 30 0.523 599 0.500 000 0.577 350 4.72 10.27
References in periodicals archive ?
Figure 11 shows Surface A as a three-dimensional view supplemented by a plan view, the latter clearly indicating the rotation a of the principal plane of symmetry.
It is interesting to note that a purely real root can still be found even when the principal plane of symmetry of each surface is no longer parallel with the G- or H-axes.
12 is the optimized radiation patterns of the principal planes.
The patterns of the principal planes are close to the desired pattern.
The radiation patterns must be quasi-isotropic in all the principal planes and, in many applications, should have a wide frequency bandwidth.
Figure 1 shows the free-space 840 MHz vertically and horizontally polarized radiation patterns in the principal planes of a conventional helical antenna, which is mounted on a cellular telephone and vertically orientated.
The measured radiation patterns of the proposed wideband CP antenna in two principal planes (x-z plane and y-z plane shown in Fig.
The radiation pattern of the antenna in two principal planes for excitation of Probe1 and Probe2 is illustrated in Figs.
For such antennas, the cross-polar level is low in the principal planes so the total power S([Theta],[Phi]) is almost equal to the power in the co-polar component.
Figures 10 and 11 show a comparison of the simulated and measured gain patterns in the elevation and azimuth principal planes.
Mesh density can be made finer or coarser by increasing (or decreasing) the number of cells between the principal planes.
The main-beam patterns and the half-power beamwidths are nearly the same at both frequencies for both principal planes to within 10 percent.

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