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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

Basic Laser Science Projects

    The Laser science projects on this page are at the basic level and require a minimum of equipment and parts to construct.

 

Measurement of small angles using a laser as an optical lever

    In this set-up the laser beam is sent from the laser to a mirror about 1 meter away from the laser then reflected back to a ruler located next to the laser [see diagram]. When a laser is reflected by a mirror placed in its beam at a forty five degree angle, the beam is deflected 90 degrees as the angle of reflection is two times the angle of incidence. If the mirror [M1 in the diagram] is rotated one degree the beam will be deflected two degrees causing the spot to move on the ruler.

PARTS
A HeNe or diode laser [you can use a laser pointer]
A ruler calibrated in mm
A mirror [preferably front surface]

Measurement of small angles diagram

  • If you measure the distance the spot moved on the ruler can you derive a formula that will tell you how much the mirror has moved in degrees?
  • What would be the maximum resolution [accuracy] of this system and what are the limiting factors on resolution?
  • Can you list some applications for an optical lever device that can measure angular displacement with great accuracy?

 

Laser range finder

    A range finder is a device that allows you to find the distance from your position to an object without using a measuring tape.

PARTS
A HeNe or diode laser [you can use a laser pointer]
A 50/50 beam splitter [you can substitute a microscope slide but it will not work as well as a beamsplitter]
A protractor and a short rod or piece of metal to make an indicator
A mirror [preferably front surface]
A board a little longer than 1 meter to mount the laser and optics

    For this set-up (see diagram) you should mount the laser on a piece of board or plywood a little longer than one meter. Mount a 50/50 beam splitter in front of the laser to split the beam into two beams. You can use a microscope slide but it will not split the beam brightness exactly in half, the transmitted beam will be brighter than the reflected beam. The beam from the beamsplitter must be deflected at exactly 90 degrees from the incoming laser beam - this is the reference beam.
   Now mount the mirror one meter away from the beamsplitter on a post that allows it to rotate - this is the probe beam . You should attach an indicating arm to the post and mount a protractor or degree scale so you can measure how many degrees the mirror has been rotated. Adjust the scale so that it reads zero when the two beam are parallel. This is easiest to do if you point the range finder at a wall three to four meters away and measure that the spots from the two beams are one meter apart. You can then adjust the indicating arm on the protractor to read zero degrees.
    Place an object at an unknown distance (X) from the range finder and adjust the object so that the laser spot from the reference beam is clearly visible on the object. Now adjust the movable mirror so that the probe beam is exactly overlaid on the reference beam (the two spots are on top of each other). You can now read off the displacement of the mirror in degrees from the protractor.

Laser rangefinder project diagram

  • What type of triangle do the beams of the range finder form?
  • Given the reading in degrees, how would you derive a formula that would allow you to measure the distance to the object?
  • What would be the maximum and minimum distances that the range finder would be accurate?
  • What modifications would you make if you wanted to measure shorter distances? Longer distances?
  • What applications would a device like this have?
  • What is the theoretical accuracy of this range finder and what are the factors that limit it's resolution?

 

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 a number of on-line sources, 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 many sources such as AV companies and stores like Office Depot, Office Max, Radio Shack and Staples.
   Optics parts such as front surface mirrors and beamsplitters can be obtained from optics vendor, as well as from some electronics surplus houses.

 

[ 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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