Fundamentals of Imaging Tao Zhou Chapter 1 Light

Fundamentals of Imaging Tao Zhou Chapter 1 Light Source 1. 1 Different kind of light sources and their mechanisms 1. 2 Intensity and color of light sources

1. 1. 1 Blackbody radiation More frequency more modes

Blackbody radiation radiated power per unit area

Wien's Displacement Law

Solar Iradiance

Blackbody radiation Red hot is not that hot! T is only about 1000 K Volcano’s lava with varying T !

Human body radiation Essentially all of the radiation from the human body and its ordinary surroundings is in the infrared portion of the electromagnetic spectrum, which ranges from about 1000 to 1, 000 on this scale.

Cosmic microwave background

The first man-made heat radiation source

The first modern heat radiation source Incandescent lamp T=?

1. 1. 2 Light from gas discharge tubes Neon light Fluorescent lamps

The structure of a fluorescent lamp

Hg atoms, once excited, emit UV light

Last step: Fluorescence from phosphor UV absorbed, Visible emitted

Typical fluorescent light spectrum

What is the difference between fluorescent lamps and other gas discharge lamps such as neon lamp? Light come from fluorescence Light come directly from gas ion emission

1. 1. 3 Solid State Source LED: Light emitting diode

What is a diode?

Biased Diode Forward bias

How is light produced in LED Forward bias

LED Characteristics

White LED

LEDs have all 3 colors and are widely used now

Lighting Spectra Fluorescent White LED Quartz-Halogen Metal Halide

1. 1. 4 Laser Quantum Properties of Light

Population Inversion Coherent Light Parallel Light Monochromatic Light

Laser type Gas Laser He-Ne CO 2 Ar

Laser type Laser Diode Type Peak Power Wavelength Application Ga. As 5 m. W 840 nm CD Players Al. Ga. As 50 m. W 760 nm Laser printers 1300 nm Fiber communications Ga. In. As. P 20 m. W

Laser type Solid State Laser Ruby, Nd: YAG, Nd: Glass, etc. Ruby Laser