Introduction to Nonimaging Optics, 2nd Edition

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Why Use Nonimaging Optics

1.1 Area and Angle

Typically, optical systems have an emitter (light source) E which emits light, an optic O which deflects it, and a receiver (target) R which is illuminated by it, as shown in Figure 1.1.

As light travels in space, or through an optic, it spreads over some area, and also over some angle. Area and angle are related and that is the basis for illumination optics. Figure 1.2 shows some flashlights emitting light downwards. In Figure 1.2a, the flashlights emit light toward a large area a₁. The angular aperture θ₁ of the light crossing a₁ is small. In Figure 1.2b, the same flashlights now emit light toward a small area a₂. The angular aperture θ₂ of the light crossing a₂ is now large. The reason ...