Luneberg Lenses

The Luneberg lens is scientifically recognized. It is used to enhance the radar visibility of a target upon which it is installed. For example a sailboat with a Luneberg lens reflector upon it might appear on a radar screen as a large ship, or a target drone might appear as large as an airplane.

Fig 1 Signal Path in the Luneberg Lens

A Luneberg lens is spherical, consisting of a number of concentric spherical dielectric shells (hemispherical shells in the case of TriLens reflectors). Each shell has a different index of refraction, so that an entering signal will be refracted into a nearly elliptical path to a point on the opposite surface of the sphere (Figure 1). A reflective material located at the opposition point causes a return of the signal, again refracted elliptically through the sphere and out again in the direction it came.

A Luneberg lens performs much as a parabolic reflector, except that whereas a parabolic reflector is effective along its central axis (M), the Luneberg lens is an effective retroreflector over a wide range of entry angels (such as PIXI to P"X" in Figure 1, for example). The performance in this respect is limited only by the practical limitations of the reflector geometry.

Fig 2. Elliptical Path in the Luneberg Lens

The result is a completely passive, reflective device, which concentrates the reflected energy back in the direction of the incident beam. The Luneberg lens reflector is built with a spherically shaped reflector cap as shown in figure 2, indicated by the letter AL Normally these reflectors will have a conical reflective pattern, with the horizon cone subtending 120 degree at the MB points. TriLens Radar Reflector Luneberg lenses are designed for optimum use with a X-band radar, but they are broad-band devices and also provide useful performance at other radar frequencies. TriLens Radar Reflector Luneberg lenses are manufactured to meet military specifications for use in military, naval, aeronautical and other rigorous applications.

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