chapter 2, Optics Fundamentals

from: Infrared Optics and Zoom Lenses, Second

Author(s): Allen Mann

Published: 27 March 2009

Chapter DOI: 10.1117/3.829008.ch2

Chapter Page Count: 12 pages

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Front Matter

1. System Considerations

2. Optics Fundamentals

3. Unique Features of the Infrared Region

4. Optical Design Techniques

5. Zoom Lenses

6. Refractive Infrared Zoom Lenses

7. Reflective Infrared Zoom Systems

8. Future Trends

9. Summary of Applications

A. Miscellaneous Patents

B. Computer Analysis of Selected Patents

C. Answers to Problems from Chapter 2

Back Matter

Preview

Chapter Contents

2.1 Lens Equation
2.2 Stops and Pupils
2.3 Optical Formulas
2.4 Optical Performance Criteria
2.5 Telescopes
2.6 Primary Aberrations
2.6.1 Definition of the Seidel aberrations
2.6.2 Variation of primary aberrations with aperture and field height
2.6.3 Stop shift equations
2.7 Achromatism
2.7.1 Primary achromatism
2.7.2 Secondary spectrum
2.8 Principal Planes
2.9 Problems
2.10 References

Excerpt

2.1 Lens Equation

The basic lens equation is illustrated in Fig. 2.1 and can be stated as

where f is the effective focal length, l is the object distance, and l′ is the image distance. In Fig. 2.1, l is negative and l′ is positive, in accordance with the sign convention. The focal length f = 1∕P, where P is the power of the lens. For example, if l = −1 and l′ = +1, then P = 2 and f = 0.5.

An important special case of the lens equation is illustrated in Fig. 2.2. This is when the object is assumed to be at infinity, as is the case in most infrared zoom lens applications. In accordance with Eq. (2.1), 1∕l = 0, f = l′, and the image plane lies in the focal plane of the lens. In the above example, f = l′ = 0.5.

2.2 Stops and Pupils

The aperture stop is the limiting aperture of the optical system. The aperture stop for a simple lens is shown in Fig. 2.3. The entrance pupil is the image of the aperture stop in object space and is coincident with it. The exit pupil is the image of the aperture stop in image space and is also coincident with the aperture stop in the figure. The field stop limits the size of the detector at the image plane.

DOI: 10.1117/3.829008.ch2

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