Computational Colour Science Using MATLAB, 2nd Edition

Chapter 12

Multispectral Imaging

12.1 Introduction

The characterisation of a digital colour camera so that the device-dependent RGB values may be transformed to device-independent coordinates such as XYZ values effectively converts the camera into an imaging colorimeter and this has many practical uses. However, in imaging science, there are limitations to this approach. Many applications require that some illuminant-independent measure, such as the spectral reflectance values, be determined at each pixel location in a scene and this may be achieved by using an imaging spectrophotometer. Although imaging spectrophotometers are becoming more commercially available, they are often expensive and there is current interest in exploring to what extent spectral values may be recovered from a standard three-channel camera system or from a camera system with relatively few channels. The term multispectral imaging is sometimes used to define this field of research. This definition is confusing, however, since even the normal RGB image representation may be described as being multispectral in some sense. In this chapter, however, the term multispectral imaging will be used to define techniques and methods that may be used to recover spectral information from camera systems with a small number of channels (typically in the range 3–8). We distinguish multispectral imaging from the term hyperspectral imaging which we use to describe techniques where spectral values are measured using imaging ...