topic 2 - overview of image acquisition and processing systems digital image processing course 3624...
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Topic 2 - Overview of Image Acquisition and Processing Systems
DIGITAL IMAGE PROCESSING
Course 3624
Department of Physics and Astronomy
Professor Bob Warwick
Digital Image Processing
• Digital Image Processing (DIP) is the use of computer software to manipulate, process and display images stored in a digital format on a computer system.
• The basic elements of an “end-to-end” DIP system are:
Scene
Imaging System
Image Acquisition System
2.1 Imaging and PhotometryScene intensity (W/m2/ster)
Flux density in the image (W/m2)
Flens
Scene Focal Plane
Solid angle subtended (steradians)
D Diameter of lens (m)
F♯ = Flens / D Lens Focal Ratio
If the source image has an area (Flens )2 then its flux density (W/m2) is:
The light source in the scene produces
a flux density incident on the lens of:
The light flux collected (W) is :
♯
source
Industry Standard Quantities and Units
Luminous Flux = Radiant Power = Flux
1 lumen = (1/683) W @ 555nm
Illuminance = Flux Density
1 lux = 1 lumen/m2
Luminance = Surface Brightness = Intensity
1 candela/m2 = 1 cd/m2 =1 lumen/m2/ster
but we will not use these further....
2.2 The Image Acquisition System
The Image Acquisition System converts the 2-d (analogue) light distribution into a 2-d array of stored numbers, i.e., the Digital Image.
Such systems consists of three elements:•The Focal Plane Detector(s)•The Analogue-To-Digital Converter•The Image Buffer
ADC p bitsImage Buffer
Analogue Voltage
from Detector
Convert Pulse
To Data Store or Computer
Colour Information in the Scene
So far we have only considered monochrome i.e., single waveband imaging. More generally:
W/m2/ster/Hz
W/m2/ster/m
In practical systems a waveband filter is included to restrict the EM frequency/wavelength range of the detected signal. Then with a filter of response
♯
W/m2
Geometric Factor Spectral Response
Forming a colour image from three “monochrome” inputs
Eg. Colour Televison, Digital Cameras, Human Eye etc..
Recorded Images
Reconstructed Image
Sensor Architecture
Display Architecture
Reconstructing colour images on a CRT or LCD Display
Reconstructing colour images on a CRT or LCD Display
2.3 The Image Processing System
Image Processing Software System
Digital Image Input
•Workstation
•High Resolution Display
•Data Storage Devices (disk etc.)
•Hardcopy Printer
Hardware Software
This course looks at various sorts of processes and algorithms that can be implemented in the
Image Processing Software.