Book contents
- Frontmatter
- Contents
- Preface
- Symbols, signs and other conventions
- Part I General theory
- 1 Introduction
- 2 Image formation and ray tracing
- 3 Paraxial theory of refracting systems
- 4 Paraxial theory of reflecting optics
- 5 Non-Gaussian optics: Introduction to aberrations
- 6 Simple lens types, lens systems and image formation
- 7 Mirror types and image formation
- 8 Prisms
- 9 Aperture stops and pupils, field lenses and stops
- 10 Defocus, depth-of-field and focussing techniques
- 11 Basic optical metrology
- 12 Photometry of optical systems
- Part II Geometrical optical instruments or systems
- Part III Physical optics and physical optical instruments
- Part IV Ophthalmic instruments
- Part V Aberrations and image quality
- Part VI Visual ergonomics
- Appendices
- Index
5 - Non-Gaussian optics: Introduction to aberrations
Published online by Cambridge University Press: 13 January 2010
- Frontmatter
- Contents
- Preface
- Symbols, signs and other conventions
- Part I General theory
- 1 Introduction
- 2 Image formation and ray tracing
- 3 Paraxial theory of refracting systems
- 4 Paraxial theory of reflecting optics
- 5 Non-Gaussian optics: Introduction to aberrations
- 6 Simple lens types, lens systems and image formation
- 7 Mirror types and image formation
- 8 Prisms
- 9 Aperture stops and pupils, field lenses and stops
- 10 Defocus, depth-of-field and focussing techniques
- 11 Basic optical metrology
- 12 Photometry of optical systems
- Part II Geometrical optical instruments or systems
- Part III Physical optics and physical optical instruments
- Part IV Ophthalmic instruments
- Part V Aberrations and image quality
- Part VI Visual ergonomics
- Appendices
- Index
Summary
Introduction
Paraxial optics only gives a guide to the image formation by real optical systems. Real imagery is different from the ideal or Gaussian model because of the effects of aberrations and diffraction. Both of these cause the light distribution in the image space, and most importantly in the Gaussian image plane, to be different from that in the object space or plane. Whereas diffraction can only be explained in terms of physical optics, aberrations can be discussed in terms of either geometrical or physical optics. As a general rule, geometrical optics only adequately describes the image plane light level distribution on a coarse scale and this is only accurate in highly aberrated systems. On the other hand, physical optics is more accurate than geometrical optics and so better describes the light level distribution on a fine scale, which is particularly important when the aberrations are small or zero. However, physical optical calculations are usually more complex and difficult and therefore we prefer to use the simpler geometric optical approach as often as possible.
Aberrations may be defined as the factors which cause the departure of real rays from the paths predicted by Gaussian optics. They may be investigated by following the paths of real rays through an optical system, using some suitable ray tracing procedure (e.g. the one described in Section 2.3 of Chapter 2) and comparing their paths with the paths of equivalent paraxial rays.
Aberration of a beam
Beams, not single rays, form images and therefore the quality of an image depends upon the combined aberrations of all the rays in the beam.
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- The Eye and Visual Optical Instruments , pp. 97 - 130Publisher: Cambridge University PressPrint publication year: 1997