Jump to Content
Your Recent History
View Cart
SUBSCRIPTIONS & PRICING
GENERAL INFORMATION
chapter 3, Unique Features of the Infrared Region
Table of Contents
- 5. Zoom Lenses
Chapter Contents
- 3.1 Optical Materials
- 3.1.1 Materials for the infrared
- 3.1.2 Calculation of index of refraction
- 3.2 Thermal Compensation
- 3.2.1 Focus shift with temperature
- 3.2.2 Athermalization
- 3.2.3 Athermalization methods
- 3.3 Cold Stop and Cold Shield
- 3.4 Narcissus
- 3.4.1 Types of retroreflections
- 3.4.2 Reduction techniques
- 3.5 Glass Substitution
- 3.6 References
Excerpt
3.1 Optical Materials
3.1.1 Materials for the infrared
A large number of optical materials transmit in the infrared region of the spectrum. However, the list of materials is quite limited when one considers physical characteristics, workability, and cost. Table 3.1 indicates the materials most commonly used in infrared zoom-lens systems for the 3- to 5-μm and 8- to 12-μm regions. It is apparent that indices of refraction are higher than they are for optical materials in the visible spectrum. This is an advantage in the correction of third-order and higher-order aberrations. For example, with a lens shaped for minimum spherical aberration, the angular spherical aberration βSPH for an object at infinity can be expressed by
, or 
. The variation with a refractive index can readily be seen by tabulating β for an f∕1 lens as an example in Table 3.1. The advantage of using a high-index material like silicon or germanium is quite apparent from these calculations.
©2009 Society of Photo-Optical Instrumentation Engineers
DOI: 10.1117/3.829008.ch3
Your library does not subscribe to the eBooks portion of the SPIE Digital Library.
PURCHASE CHAPTER ($US12)
SPIE Digital Library
This Publication
Google Scholar
PubMed