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Introduction

Bibliography

Glossary of Terminology

Laser safety overview

Other applications of lasers

Selected laser related web sites

Basic laser science projects

Intermediate laser science projects

Advanced laser science projects

Illustrations for laser science projects

 
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Laser Science Projects

 Advanced Laser Science Projects

    The Laser science projects on this page are at the advanced level and require more equipment and parts as well as some knowledge of electronics to construct.  They are more complex than the than the basic and intermediate projects.

 

Demonstration of the principals of bar code scanning

    The UPC (Universal Product Code) code is a series of bars or lines that are printed onto many products and identify the product with a unique serial number.  This is a more advanced project as it requires some knowledge of, and skill with, electronics.

PARTS
A HeNe or diode laser (you can use a laser pointer)
A photocell or phototransistor
A circuit to detect and amplify the output of the detector/transistor
A way to display the output of the circuit such as a LED or a meter

  First mount the phototransistor into a short length (2 to 3 cm) of black plastic tube to form a light shield.  Now place the laser at a slight angle to a slit in a piece of cardboard or opaque plastic so that you can drag a UPC code past the slit. Place a piece of white paper over the slit and point the laser at the paper; then point the phototransistor at the laser spot, adjusting the angle of the phototransistor (and the sensitivity of the amplifier circuit) until you get the maximum signal.
   Make a test UPC symbol by Xeroxing one from a product with an enlarging copier so it is 4 or 5 times larger than the original - this will simplify your experiment.

UPC bar code scanning diagram

  • If you drag the test UPC code past the slit, what do you see on the meter or LED?
  • What is the optical principal at work here?
  • How can you adjust the circuit or modify it to improve the output?
  • What improvements can you make to the basic design to increase the light gathering of the phototransistor?
  • What improvements can you make to this project to reduce interference from room light?
  • How can you modify the output from the phototransistor and detector circuit to provide more useful information from the UPC code?
  • What other applications can you think of for this type of technology?

 

Laser "burglar alarm"

   A laser beam can be used a a "burglar alarm" to detect unauthorized access.  This is a more advanced project as it requires some knowledge of, and skill with, electronics.

PARTS
A HeNe or diode laser (you can use a laser pointer)
Three (or more) small mirrors on mounting brackets
A photocell or phototransistor
A circuit to detect and amplify the output of the detector/transistor
A device such as a bell or siren to provide the alarm signal

    First mount the phototransistor into a short length (2 to 3 cm) of black plastic tube to form a light shield.  Now mount the small mirrors around the doorway or other opening to be protected as shown in the diagram (only 3 mirrors are shown, you can use more).  Mount the laser so that the beam is deflected back and forth across the opening by the mirrors and into the photo detector.
   You will need to create an electronic circuit that will amplify the output of the photocell or photo transistor.  The output needs to be set up in such a way that it is on when the beam is off (and vice versa).  The output needs to be sufficient so that it can drive the bell, buzzer or siren you are using to give the alarm.  When the beam is broken, the alarm should sound.

Laser burglar alarm diagram

  • What is the optical principal at work here?
  • What improvements can you make to the basic design to increase the light gathering of the phototransistor?
  • How can you adjust the circuit or modify it to improve the output?
  • What improvements can you make to this project to reduce interference from room light or sunlight?
  • What methods can you devise to defeat this kind of device?
  • What methods can you devise to improve the performance of this kind of device or make it more difficult to defeat?
  • What other applications can you think of for this type of technology?

 

Parts Sources
   
The most important part you will need is a laser. Most High School science departments will have a HeNe laser and you may be able to use it - ask your teacher. You can also obtain HeNe lasers from on-line vendors, from surplus houses, and from ads in electronics magazines.
   You can use a 'laser pointer' for these projects - small pen shaped devices with a laser diode mounted in one end.  These are available from on-line vendors, AV companies and even stores like Office Depot, Office Max, Radio Shack and Staples.
   Optics parts such as front surface mirrors and beamsplitters can be obtained from on-line vendors as well as from some electronics surplus houses.
    Electronics parts can be obtained from suppliers such as Radio Shack or a local electronics vendor.
    Simple mounts for the parts or mirrors can be fabricated from wood or angle brackets obtainable form hardware vendors such as Home Depot or Builders Square.

[ Introduction | Bibliography | Glossary of Terminology | Laser safety overview | Other applications of lasers | Selected laser related web sites | Basic laser science projects | Intermediate laser science projects | Advanced laser science projects | Illustrations for laser science projects ]

 

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