chapter 12, Lux Transfer

from: Photon Transfer

Author(s): James R. Janesick

Published: 14 August 2007

Chapter DOI: 10.1117/3.725073.ch12

Chapter Page Count: 19 pages

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Front Matter

1. Introduction

2. Photon Interaction

3. Photon Transfer Noise Sources

4. Photon Transfer Theory

5. Photon Transfer Curve

6. e⁻/DN Variance

7. Nonlinearity

8. Flat Fielding

9. Modulation Photon Transfer

10. Signal-to-noise Performance

11. Read Noise

12. Lux Transfer

A. PTC Data Reduction Example

B. PTC Simulation Program with Thermal Dark Current

C. PTC Simulation Program with FPN Removal through Flat Fielding

D. LTC Simulation Program with Thermal Dark Current

Back Matter

Preview

Chapter Contents

12.1 Introduction
12.2 Minimum Detection Limit
12.3 Responsivity
12.4 Modulation LTC
12.5 Acceptable Image
12.6 LTC Ratio
12.7 LTC Data Sequence

Excerpt

12.1 Introduction

A lux transfer curve (LTC) is a powerful extension of PTC, whereas a PTC is generated with an uncalibrated light source, and a LTC utilizes an absolute light source. Therefore, LTC characterizes a camera system in absolute terms. For example, commercial camera sensitivity is often quoted in terms of “minimum detection limit” at an illumination level typically specified in units of lux. LTC will produce this figure-of-merit parameter in addition to other absolute performance parameters.

A LTC is based on the relation

where [S/N]_{A_FF} is the absolute flat-field S/N performance, and

which is the absolute signal (e⁻), where f# and m are the f number and magnification of a lens above the imager, T_L is the transmission of the lens, L is the luminance light level emitted from a Lambertian diffuse surface that overfills the collection lens (or detector if a lens is not used) given in lux, and N_L is the number of photons/cm²-sec for one lux. For example, the number of photons at a 0.550-μm wavelength (green) for one lux is 4.02 × 10¹¹ photons/cm²-sec. Discussions below assume this wavelength to be a standard.

Signal can also be expressed in radiometric units as

where N_P is photons/cm²/sec at a specific wavelength.

The following examples demonstrate how LTCs are generated and applied using the relations above. A simulation computer program used to create LTCs is presented in Appendix C as a reference.

DOI: 10.1117/3.725073.ch12

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