chapter 9, Petzval Lenses and Telephoto Objectives

from: Fundamental Optical Design

Author(s): Michael J. Kidger

Published: 12 December 2001

Chapter DOI: http://dx.doi.org/10.1117/3.397107.ch9

Chapter Page Count: 15 pages

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Front Matter

1. Geometrical Optics

2. Paraxial Optics

3. Ray Tracing

4. Aberrations

5. Chromatic Aberration

6. Seidel Aberrations

7. Principles of Lens Design

8. Achromatic Doublet Objectives

9. Petzval Lenses and Telephoto Objectives

10. Triplets

11. Eyepieces and Afocal Systems

12. Thermal Imaging Lenses

13. Catadioptric Systems

Back Matter

Preview

Chapter Contents

9.1 Seidel analysis
9.1.1 Calculation of predicted transverse aberrations from Seidel coefficients
9.2 Optimization
9.3 Examples
9.3.1 Simple Petzval lens with two doublets
9.3.2 Petzval lens with curved image surface
9.3.3 Petzval lens with field flattener
9.4 The telephoto lens

Excerpt

The doublets described in the last chapter are limited to small apertures (up to about f/4) and a small field of view. If we require a larger field angle and aperture then the Petzval lens, which consists of two positive groups separated by an air space, is a simple solution. Joseph Petzval designed his famous “Portrait Lens” in 1839. The front lens was a cemented doublet, the rear component an air-spaced doublet. This was probably the first lens ever to be designed by computation, in this case by logarithmic tables.

The limitation of the doublet objective is that astigmatism cannot be corrected in a single component, and this severely limits the field angle that it can cover. We have seen from earlier chapters that for a thin lens at the stop, the astigmatism is given by

which must always be non-zero. Hence, astigmatism can only be corrected if there are one or more lenses that are not at the stop. Thus, two separated lenses, as shown in the Fig. 9.1, may be employed to generate equal and opposite amounts of astigmatism. In practice, these will not always be single lenses, but achromatic doublets or more complex combinations.

http://dx.doi.org/10.1117/3.397107.ch9

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