l'image de fond

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General Informations

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We find the use of imaging in a considerable number of areas. We find in the life of everyday on our computers, magazines or our cameras. But also in scientific applications for observing the very small (Scanning Electron Microscope SEM) or to see the infinitely large with the Huble satellite for example. The medical industry is very greedy images showing the inside of human body without open it, everyone knows the X-ray images, the PET (Positron Emission Tomography), MRI (Magnetic Resonance Imaging) or even CAT (Computer-Aided Tomography).

What are exactly a digital image?

It is a physic represantation in a 2D matrix shape where each coordinate of the matrix represents the intensity of the physical quantity measured by a sensor to a surface of the environment, depending of the sensor surface, of number of pixels and the distance of the object observed. Each sensor is created to observe a bandwidth of electromagnetic radiation. These electromagnetic waves are defined according to their wavelengths, they are calculated as
Lamda = V/F where Lamda is the wavelength in metter, V the velocity in m/s and F the frequency of wave in Hertz
for the electromagnetic waves, the speed of travel is the speed of light c (Celeritas) to 299,792,458 m / s. We get a simple calculation:
Lamda = 300/F where F is in MHz.

wave kindFrequency (Hz)Wavelength (m)
radio wave 3.107 > 10
Radar wave3.107 3.10810 1
Microwave3.108 3.10111 1-3
Infrared3.1011 3.10141-3 1-6
Visible Light3.1014 3.10151-6 1-7
Ultraviolets3.1015 3.10161-7 1-8
X Ray 3.1016 3.1019 1-8 1-11
Gamma Ray 3.107191-11

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