chapter 2, Propagation of Optical Radiation

from: The Art of Radiometry

Author(s): James M. Palmer, Barbara G. Grant

Published: 15 December 2009

Chapter DOI: 10.1117/3.798237.ch2

Chapter Page Count: 50 pages

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Front Matter

1. Introduction to Radiometry

2. Propagation of Optical Radiation

3. Radiometric Properties of Materials

4. Generation of Optical Radiation

5. Detectors of Optical Radiation

6. Radiometric Instrumentation

7. Radiometric Measurement and Calibration

A. Système International (SI) Units for Radiometry and Photometry

B. Physical Constants, Conversion Factors, and Other Useful Quantities

C. Antiquarian's Garden of Sane and Outrageous Terminology

D. Solid-Angle Relationships

E. Glossary

F. Effective Noise Bandwidth of Analog RC Filters and the Selection of Filter Parameters to Optimize Signal-to-Noise Ratio

G. Bandwidth Normalization by Moments

H. Jones Near-Small-Source Calibration Configuration

I. Is Sunglint Observable in the Thermal Infrared?

J. Documentary Standards for Radiometry and Photometry

K. Radiometry and Photometry Bibliography

L. Reference List for Noise and Postdetection Signal Processing

Back Matter

Preview

Chapter Contents

2.1 Basic Definitions
2.1.1 Rays and angles
2.1.2 System parameters
2.1.3 Optical definitions
2.2 Fundamental Radiometric Quantities
2.2.1 Radiance
2.2.2 Radiant exitance
2.2.3 Irradiance
2.2.4 Radiant intensity
2.3 Radiometric Approximations
2.3.1 Inverse square law
2.3.2 Cosine³ law
2.3.3 Lambertian approximation
2.3.4 Cosine⁴ law
2.4 Equation of Radiative Transfer
2.5 Configuration Factors
2.6 Effect of Lenses on Power Transfer
2.7 Common Radiative Transfer Configurations
2.7.1 On-axis radiation from a circular Lambertian disc
2.7.2 On-axis radiation from a non-Lambertian disc
2.7.3 On-axis radiation from a spherical Lambertian source
2.8 Integrating Sphere
2.9 Radiometric Calculation Examples
2.9.1 Intensities of a distant star and the sun
2.9.2 Lunar constant
2.9.2.1 Calculation
2.9.2.2 Moon-sun comparisons
2.9.3 “Solar furnace”
2.9.4 Image irradiance for finite conjugates
2.9.5 Irradiance of the overcast sky
2.9.6 Near extended source
2.9.7 Projection system
2.10 Generalized Expressions for Image-Plane Irradiance
2.10.1 Extended source
2.10.2 Point source
2.11 Summary of Some Key Concepts
For Further Reading
References

Excerpt

2.1 Basic Definitions

2.1.1 Rays and angles

A ray is represented by a vector: a straight line indicating the magnitude and direction of propagation. A wavefront is a notional surface locally normal to a ray. Thus, a wavefront could be a plane (all rays parallel, as if from infinity) or a curved surface (indicating diverging rays, as if emanating from a point). Figure 2.1 illustrates rays and wavefronts for both cases.

A beam can be defined by two separated elements of area as shown in Fig. 2.2. It is thus the locus of possible rays that pass through the two areas separated by distance d. As dA₁ and dA₂ approach zero, the beam approaches a single ray. Since there is a small, but nevertheless finite, cross-sectional area associated with a beam, it is capable of carrying power without the flux density (power per unit area) approaching infinity.

DOI: 10.1117/3.798237.ch2

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