5.1 Optics in the Imaging Chain

Optics is the discipline of physics that studies the properties of light, including the propagation of light and the interaction of light with matter. Our interest here is in modeling the distribution of the light at the sensor of the camera in the imaging chain (Fig. 5.1). The optical elements of the camera shape the electromagnetic energy into the image that is formed on the sensor. Modeling the propagation of the electrometric waves through the optical elements is critical to understanding the quality of the image that is formed. Figure 5.1 Modeling the optics describes the distribution of light onto the sensor in the imaging chain.

5.2 Geometric and Physical Optics

The two most common models for describing the propagation of light are geometric optics and physical optics. Geometric optics is a simplified model that describes light propagation in terms of rays. Each ray is drawn in the direction of radiant energy flow as it propagates and interacts with matter. The geometric model greatly simplifies calculations of basic optical behavior, such as reflection and refraction.¹ The law of reflection is easily illustrated using geometric optics (Fig. 5.2) and states that light reflecting from a surface will have the angle of incidence θ_i equal to the angle of reflection θ_r, given by

(5.1)

Snell's law (Fig. 5.3) gives the relationship between the angle of incidence θ₁ of the light in the first medium with an index of refraction n₁ and the angle of refraction θ₂ of the light in the second medium having an index of refraction n₂, and is given by

(5.2)