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:

• Image focused onto a photoconductive target.
  
• Target scanned line by line horizontally by an electron beam
  
• Electric current produces as the beam passes over target.
  
• Current proportional to the intensity of light at each point.
  
• Tap current to give 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

--

• unwanted persistence between one frame and the next
  
• Non-linear video output with respect to light intensity.
  
• Non-flat target on tube.

CCD Camera

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

• Single IC device
  
• Consists of an array of photosensitive cells
  
• each cell produces an electric current dependent on the incident light falling on it.
  
• Video Signal Output
  
• Less geometric distortion
  
• More linear Video output.