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2D Image Input

The basic two-dimensional image is a monochrome (greyscale) image which has been digitised.

Describe image as a two-dimensional light intensity function f(x,y) where x and y are spatial coordinates and the value of f at any point (x, y) is proportional to the brightness or grey value of the image at that point.

A digitised image is one where

For computational purposes, we may think of a digital image as a two-dimensional array where x and y index an image point. Each element in the array is called a pixel (picture element). See Figs. 30 and 31.

 

Fig. gif Greyscale image and highlighted region

  figure2663
Figure: Pixel values in highlighted region

2D Input Devices

TV Camera or Vidicon Tube

A first choice for a two-dimensional image input device may be a television camera -- output is a video signal:

This form of device has several disadvantages.

Limited resolution
-- finite number of scan lines (about 625) and frame rate (30 or 60 frames per second)
Distortion
--

CCD Camera

By far the most popular two-dimensional imaging device is the charge-coupled device (CCD) camera.

Frame Stores

Video Signal must be digitised.

A device known as a frame storeor frame grabber usually performs this task. It:


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Next: 3D imaging Up: Image Acquisition Previous: Image Acquisition

dave@cs.cf.ac.uk