principal plane

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prin·ci·pal plane

the theoretic plane of a compound lens system. See: principal point.
Farlex Partner Medical Dictionary © Farlex 2012


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)enlarge picture
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)sine
tangent valueerror (%) sine errorerror (%) tangent error
0.50.008 7270.008 7270.008 7270.000.00
10.017 4530.017 4520.017 4550.010.01
20.034 9070.034 8990.034 9210.020.04
30.052 3600.052 3360.052 4080.050.09
40.069 8130.069 7560.069 9270.080.16
50.087 2660.087 1560.087 4890.130.25
60.104 7200.104 5280.105 1040.180.37
70.122 1730.121 8690.122 7850.250.50
80.139 6260.139 1730.140 5410.330.65
100.174 5330.173 6480.176 3270.511.03
150.261 7990.258 8190.267 9491.152.35
5200.349 0660.342 0200.363 9702.064.27
300.523 5990.500 0000.577 3504.7210.27
Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann
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.
Figure 11 compares the simulated and measured ARs against frequency in the two vertical principal planes ([phi] = 60[degrees] and [phi] = 150[degrees]) defined in the aforementioned section in n = 0 mode.
(8) and (9), the radiation patterns of the principal planes have been computed, and the results given by the AEP method and CST simulation are shown in Fig.
The half-power beamwidths as a function of frequency of the antenna in the principal planes are depicted in Figure 11.
Good broadside radiation patterns with low cross polarizations (Less than 23 dB) are observed in the two principal planes. From the measured results, it is found that the associated antenna parameters are in good agreement with simulation analysis.
The radiation patterns in the three principal planes are plotted in Figure 5, for selected frequencies of (3, 5, 7.5 & 10) GHz.
The simulated far-field radiation patterns at 1.5754 GHz of the two principal planes, [phi] = 0[degrees] and [phi] = 90[degrees], are shown in Figure 5.
The antenna is sensitive to both vertically and horizontally polarized waves and its radiation patterns have good isotropic characteristics in all the principal planes. The antenna could be easily shielded to reduce interaction between it and the human body.
Radiation patterns of two principal planes [phi] = 0[degrees] and [phi] = 90[degrees] in simulation are depicted in Figure 8.
The measured radiation patterns of the proposed wideband CP antenna in two principal planes (x-z plane and y-z plane shown in Fig.
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.
The radiation pattern of the antenna in two principal planes for excitation of Probe1 and Probe2 is illustrated in Figs.