Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.



Published on

  • Be the first to comment

  • Be the first to like this


  1. 1. Seeing Invisible Things <ul><li>We will find out: </li></ul><ul><li>Review the terms ‘pixel’ and ‘resolution’ </li></ul><ul><li>Understand how images can be gathered using pulses of sound or radiation </li></ul>
  2. 2. Pixel <ul><li>A pixel is a ‘Picture Element’ – it is the smallest part of the reconstructed image. </li></ul>
  3. 3. Resolution <ul><li>Resolution is smallest discernible feature or smallest detectable difference on an image </li></ul><ul><li>To calculate it: </li></ul><ul><li>Resolution = image dimension/number of pixels </li></ul><ul><li>for an image from the scale and number of pixels </li></ul><ul><li>e.g. what is the resolution of a 15cm x 10cm image made up of 15000 pixels? </li></ul>
  4. 4. Resolution <ul><li>e.g. what is the resolution of an image of a 15cm x 10cm area made up of 15000 pixels? </li></ul><ul><li>Number of pixels = Area / Pixel Size </li></ul><ul><li>Therefore Pixel Size = Area/ Number of pixels </li></ul><ul><li>Area = 15cm x 10cm = 150cm 2 </li></ul><ul><li>Number of pixels = 15000 </li></ul><ul><li>Therefore Pixel Size = 150 / 15000 = 0.01cm 2 = 1mm 2 </li></ul><ul><li>Resolution = 1mm 2 </li></ul><ul><li>This is the smallest distinguishable detail – but what if the image represented an actual area of 150m x 100m? </li></ul>
  5. 5. Resolution of an image <ul><li>This is an image of East Midlands Airport – it shows an area of 2km x 1km </li></ul><ul><li>What is the resolution if it is displayed on the screen as previously discussed? </li></ul>
  6. 6. Showing Resolution <ul><li>Using a sheet of A4 squared paper, put the picture of EMA underneath and draw around it. </li></ul><ul><li>Count the number of squares. </li></ul><ul><li>What is the resolution if the area shown in the image is 100m x 150m assuming that each square on the paper is 1 pixel? </li></ul>
  7. 7. Imaging with Sound <ul><li>Ultrasound can be used to form images </li></ul><ul><li>Pulses are sent and reflections are timed: </li></ul><ul><li>Distance = Speed x Time </li></ul><ul><li>Pulses are sent so that sound does not become ‘muddled’ – sent and reflected pulse. </li></ul>