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 Photometry Scene intensity (W/m 2 /ster) Flux density in the image (W/m 2 ) F lens SceneFocal Plane Solid angle subtended (steradians) D Diameter of lens (m) F ♯ = F lens / D Lens Focal Ratio If the source image has an area (F lens ) 2 then its flux density (W/m 2) 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) 555nm Illuminance = Flux Density 1 lux = 1 lumen/m 2 Luminance = Surface Brightness = Intensity 1 candela/m 2 = 1 cd/m 2 =1 lumen/m 2 /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 AD C p bits Image 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/m 2 /ster/Hz W/m 2 /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/m 2 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

2.3 The Image Processing System Image Processing Software System Digital Image Input Workstation High Resolution Display Data Storage Devices (disk etc.) Hardcopy Printer HardwareSoftware This course looks at various sorts of processes and algorithms that can be implemented in the Image Processing Software.