INTRODUCTION TO INFRARED (IR)
Infrared (IR) radiation is characterized by wavelengths ranging from 0.750 -1000μm (750 - 1000000nm). Due to limitations on detector range, IR radiation is often divided into three smaller regions: 0.750 - 3μm, 3 - 30μm, and 30 - 1000μm – defined as near-infrared (NIR), mid-wave infrared (MWIR), and far-infrared (FIR), respectively (Figure 1). Infrared products are used extensively in a variety of applications ranging from the detection of IR signals in thermal imaging to element identification in IR spectroscopy. As the need for IR applications grows and technology advances, manufacturers have begun to utilize IR materials in the design of plano-optics (i.e. windows, mirrors, polarizers, beamsplitters, prisms), spherical lenses (i.e. plano-concave/convex, double-concave/convex, meniscus), aspheric lenses (parabolic, hyperbolic, hybrid), achromatic lenses, and assemblies (i.e. imaging lenses, beam expanders, eyepieces, objectives). These IR materials, or substrates, vary in their physical characteristics. As a result, knowing the benefits of each allows one to select the correct material for any IR application.
Figure 1: Electromagnetic Spectrum [View Larger Image]